diff --git a/sync_diff_inspector/diff.go b/sync_diff_inspector/diff.go
index a5b2a685e..28aa4e07a 100644
--- a/sync_diff_inspector/diff.go
+++ b/sync_diff_inspector/diff.go
@@ -50,6 +50,15 @@ const (
 	checkpointFile = "sync_diff_checkpoints.pb"
 )
 
+func getSplitThreshold() int64 {
+	failpoint.Inject("binsearchSplitThreshold", func(val failpoint.Value) {
+		if threshold, ok := val.(int); ok {
+			failpoint.Return(int64(threshold))
+		}
+	})
+	return int64(splitter.SplitThreshold)
+}
+
 // ChunkDML SQL struct for each chunk
 type ChunkDML struct {
 	node      *checkpoints.Node
@@ -455,7 +464,7 @@ func (df *Diff) consume(ctx context.Context, rangeInfo *splitter.RangeInfo) bool
 		state = checkpoints.FailedState
 		// if the chunk's checksum differ, try to do binary check
 		info := rangeInfo
-		if upCount > splitter.SplitThreshold {
+		if upCount > getSplitThreshold() {
 			log.Debug("count greater than threshold, start do bingenerate", zap.Any("chunk id", rangeInfo.ChunkRange.Index), zap.Int64("upstream chunk size", upCount))
 			info, err = df.BinGenerate(ctx, df.workSource, rangeInfo, upCount)
 			if err != nil {
@@ -479,7 +488,7 @@ func (df *Diff) consume(ctx context.Context, rangeInfo *splitter.RangeInfo) bool
 }
 
 func (df *Diff) BinGenerate(ctx context.Context, targetSource source.Source, tableRange *splitter.RangeInfo, count int64) (*splitter.RangeInfo, error) {
-	if count <= splitter.SplitThreshold {
+	if count <= getSplitThreshold() {
 		return tableRange, nil
 	}
 	tableDiff := targetSource.GetTables()[tableRange.GetTableIndex()]
@@ -521,7 +530,7 @@ func (df *Diff) BinGenerate(ctx context.Context, targetSource source.Source, tab
 }
 
 func (df *Diff) binSearch(ctx context.Context, targetSource source.Source, tableRange *splitter.RangeInfo, count int64, tableDiff *common.TableDiff, indexColumns []*model.ColumnInfo) (*splitter.RangeInfo, error) {
-	if count <= splitter.SplitThreshold {
+	if count <= getSplitThreshold() {
 		return tableRange, nil
 	}
 	var (
@@ -533,7 +542,8 @@ func (df *Diff) binSearch(ctx context.Context, targetSource source.Source, table
 
 	chunkLimits, args := tableRange.ChunkRange.ToString(tableDiff.Collation)
 	limitRange := fmt.Sprintf("(%s) AND (%s)", chunkLimits, tableDiff.Range)
-	midValues, err := utils.GetApproximateMidBySize(ctx, targetSource.GetDB(), tableDiff.Schema, tableDiff.Table, indexColumns, limitRange, args, count)
+	sourceSchema, sourceTable := targetSource.GetSourceTable(tableRange)
+	midValues, err := utils.GetApproximateMidBySize(ctx, targetSource.GetDB(), sourceSchema, sourceTable, indexColumns, limitRange, args, count)
 	if err != nil {
 		return nil, errors.Trace(err)
 	}
diff --git a/sync_diff_inspector/source/mysql_shard.go b/sync_diff_inspector/source/mysql_shard.go
index 4ae410d83..4996c8fcd 100644
--- a/sync_diff_inspector/source/mysql_shard.go
+++ b/sync_diff_inspector/source/mysql_shard.go
@@ -156,6 +156,15 @@ func (s *MySQLSources) GetTables() []*common.TableDiff {
 	return s.tableDiffs
 }
 
+// GetSourceTable returns the physical source table mapped from tableDiff.
+func (s *MySQLSources) GetSourceTable(tableRange *splitter.RangeInfo) (schema string, table string) {
+	tableDiff := s.GetTables()[tableRange.GetTableIndex()]
+	if matchedSources, ok := s.sourceTablesMap[utils.UniqueID(tableDiff.Schema, tableDiff.Table)]; ok && len(matchedSources) > 0 {
+		return matchedSources[0].OriginSchema, matchedSources[0].OriginTable
+	}
+	return tableDiff.Schema, tableDiff.Table
+}
+
 func (s *MySQLSources) GenerateFixSQL(t DMLType, upstreamData, downstreamData map[string]*dbutil.ColumnData, tableIndex int) string {
 	switch t {
 	case Insert:
diff --git a/sync_diff_inspector/source/source.go b/sync_diff_inspector/source/source.go
index 9fd7106cc..4ddfbcc2a 100644
--- a/sync_diff_inspector/source/source.go
+++ b/sync_diff_inspector/source/source.go
@@ -97,6 +97,10 @@ type Source interface {
 	// GetTables represents the tableDiffs.
 	GetTables() []*common.TableDiff
 
+	// GetSourceTable returns the physical source table name mapped from tableDiff.
+	// If no route is configured, it returns the same schema/table as tableDiff.
+	GetSourceTable(*splitter.RangeInfo) (schema string, table string)
+
 	// GetSourceStructInfo get the source table info from a given target table
 	GetSourceStructInfo(context.Context, int) ([]*model.TableInfo, error)
 
diff --git a/sync_diff_inspector/source/source_test.go b/sync_diff_inspector/source/source_test.go
index 5dc614652..72d53bbb7 100644
--- a/sync_diff_inspector/source/source_test.go
+++ b/sync_diff_inspector/source/source_test.go
@@ -953,3 +953,77 @@ func TestCheckTableMatched(t *testing.T) {
 	require.Equal(t, 1, tables[1].TableLack)
 	require.Equal(t, -1, tables[2].TableLack)
 }
+
+func TestTiDBSourceGetSourceTable(t *testing.T) {
+	tableDiff := &common.TableDiff{
+		Schema: "target_schema",
+		Table:  "target_table",
+	}
+	sourceTableMap := map[string]*common.TableSource{
+		utils.UniqueID("target_schema", "target_table"): {
+			OriginSchema: "source_schema",
+			OriginTable:  "source_table",
+		},
+	}
+	tidb := &TiDBSource{
+		tableDiffs:     []*common.TableDiff{tableDiff},
+		sourceTableMap: sourceTableMap,
+	}
+	tableRange := &splitter.RangeInfo{
+		ChunkRange: chunk.NewChunkRange(nil),
+	}
+	tableRange.ChunkRange.Index.TableIndex = 0
+
+	schema, table := tidb.GetSourceTable(tableRange)
+	require.Equal(t, "source_schema", schema)
+	require.Equal(t, "source_table", table)
+
+	tidb.sourceTableMap = map[string]*common.TableSource{
+		utils.UniqueID("other_schema", "other_table"): {
+			OriginSchema: "other_schema",
+			OriginTable:  "other_table",
+		},
+	}
+	schema, table = tidb.GetSourceTable(tableRange)
+	require.Equal(t, "target_schema", schema)
+	require.Equal(t, "target_table", table)
+}
+
+func TestMySQLSourcesGetSourceTable(t *testing.T) {
+	tableDiff := &common.TableDiff{
+		Schema: "target_schema",
+		Table:  "target_table",
+	}
+	mysql := &MySQLSources{
+		tableDiffs: []*common.TableDiff{tableDiff},
+		sourceTablesMap: map[string][]*common.TableShardSource{
+			utils.UniqueID("target_schema", "target_table"): {
+				{
+					TableSource: common.TableSource{
+						OriginSchema: "source_schema_1",
+						OriginTable:  "source_table_1",
+					},
+				},
+				{
+					TableSource: common.TableSource{
+						OriginSchema: "source_schema_2",
+						OriginTable:  "source_table_2",
+					},
+				},
+			},
+		},
+	}
+	tableRange := &splitter.RangeInfo{
+		ChunkRange: chunk.NewChunkRange(nil),
+	}
+	tableRange.ChunkRange.Index.TableIndex = 0
+
+	schema, table := mysql.GetSourceTable(tableRange)
+	require.Equal(t, "source_schema_1", schema)
+	require.Equal(t, "source_table_1", table)
+
+	mysql.sourceTablesMap = map[string][]*common.TableShardSource{}
+	schema, table = mysql.GetSourceTable(tableRange)
+	require.Equal(t, "target_schema", schema)
+	require.Equal(t, "target_table", table)
+}
diff --git a/sync_diff_inspector/source/tidb.go b/sync_diff_inspector/source/tidb.go
index 6a091862e..81c76f3b0 100644
--- a/sync_diff_inspector/source/tidb.go
+++ b/sync_diff_inspector/source/tidb.go
@@ -126,7 +126,7 @@ func (s *TiDBSource) GetCountAndMd5(ctx context.Context, tableRange *splitter.Ra
 	table := s.tableDiffs[tableRange.GetTableIndex()]
 	chunk := tableRange.GetChunk()
 
-	matchSource := getMatchSource(s.sourceTableMap, table)
+	sourceSchema, sourceTable := s.GetSourceTable(tableRange)
 	indexHint := ""
 	if s.sqlHint == "auto" && len(chunk.IndexColumnNames) > 0 {
 		// If sqlHint is set to "auto" and there are index column names in the chunk,
@@ -140,7 +140,7 @@ func (s *TiDBSource) GetCountAndMd5(ctx context.Context, tableRange *splitter.Ra
 			for _, index := range dbutil.FindAllIndex(tableInfos[0]) {
 				if utils.IsIndexMatchingColumns(index, chunk.IndexColumnNames) {
 					indexHint = fmt.Sprintf("/*+ USE_INDEX(%s, %s) */",
-						dbutil.TableName(matchSource.OriginSchema, matchSource.OriginTable),
+						dbutil.TableName(sourceSchema, sourceTable),
 						dbutil.ColumnName(index.Name.O),
 					)
 					break
@@ -150,7 +150,7 @@ func (s *TiDBSource) GetCountAndMd5(ctx context.Context, tableRange *splitter.Ra
 	}
 
 	count, checksum, err := utils.GetCountAndMd5Checksum(
-		ctx, s.dbConn, matchSource.OriginSchema, matchSource.OriginTable, table.Info,
+		ctx, s.dbConn, sourceSchema, sourceTable, table.Info,
 		chunk.Where, indexHint, chunk.Args)
 
 	cost := time.Since(beginTime)
@@ -176,6 +176,16 @@ func (s *TiDBSource) GetTables() []*common.TableDiff {
 	return s.tableDiffs
 }
 
+// GetSourceTable returns the physical source table mapped from tableDiff.
+func (s *TiDBSource) GetSourceTable(tableRange *splitter.RangeInfo) (schema string, table string) {
+	tableDiff := s.GetTables()[tableRange.GetTableIndex()]
+	matchSource := getMatchSource(s.sourceTableMap, tableDiff)
+	if matchSource == nil {
+		return tableDiff.Schema, tableDiff.Table
+	}
+	return matchSource.OriginSchema, matchSource.OriginTable
+}
+
 func (s *TiDBSource) GetSourceStructInfo(ctx context.Context, tableIndex int) ([]*model.TableInfo, error) {
 	var err error
 	tableInfos := make([]*model.TableInfo, 1)
@@ -207,8 +217,8 @@ func (s *TiDBSource) GetRowsIterator(ctx context.Context, tableRange *splitter.R
 	chunk := tableRange.GetChunk()
 
 	table := s.tableDiffs[tableRange.GetTableIndex()]
-	matchedSource := getMatchSource(s.sourceTableMap, table)
-	rowsQuery, _ := utils.GetTableRowsQueryFormat(matchedSource.OriginSchema, matchedSource.OriginTable, table.Info, table.Collation)
+	sourceSchema, sourceTable := s.GetSourceTable(tableRange)
+	rowsQuery, _ := utils.GetTableRowsQueryFormat(sourceSchema, sourceTable, table.Info, table.Collation)
 	query := fmt.Sprintf(rowsQuery, chunk.Where)
 
 	log.Debug("select data", zap.String("sql", query), zap.Reflect("args", chunk.Args))
diff --git a/tests/sync_diff_inspector/router/config_base.toml b/tests/sync_diff_inspector/router/config_base.toml
new file mode 100644
index 000000000..569d2a208
--- /dev/null
+++ b/tests/sync_diff_inspector/router/config_base.toml
@@ -0,0 +1,39 @@
+# Diff Configuration.
+
+######################### Global config #########################
+
+# how many goroutines are created to check data
+check-thread-count = 4
+
+# set false if just want compare data by checksum, will skip select data when checksum is not equal.
+# set true if want compare all different rows, will slow down the total compare time.
+export-fix-sql = true
+
+# ignore check table's data
+check-struct-only = false
+
+######################### Databases config #########################
+[data-sources]
+[data-sources.tidb_up]
+    host = "127.0.0.1"
+    port = 4001
+    user = "root"
+    password = ""
+    route-rules = ["rule1"]
+
+[data-sources.mysql_down]
+    host = "127.0.0.1"#MYSQL_HOST
+    port = 3306#MYSQL_PORT
+    user = "root"
+    password = ""
+
+[routes.rule1]
+schema-pattern = "route_up_test"
+target-schema = "route_down_test"
+
+######################### Task config #########################
+[task]
+    output-dir = "/tmp/tidb_tools_test/sync_diff_inspector/output"
+    source-instances = ["tidb_up"]
+    target-instance = "mysql_down"
+    target-check-tables = ["route_down_test.t_route"]
diff --git a/tests/sync_diff_inspector/router/run.sh b/tests/sync_diff_inspector/router/run.sh
new file mode 100755
index 000000000..be0d3bbb5
--- /dev/null
+++ b/tests/sync_diff_inspector/router/run.sh
@@ -0,0 +1,37 @@
+#!/bin/sh
+
+set -ex
+
+cd "$(dirname "$0")"
+
+OUT_DIR=/tmp/tidb_tools_test/sync_diff_inspector/output
+rm -rf $OUT_DIR
+mkdir -p $OUT_DIR
+
+# prepare upstream TiDB table and downstream MySQL table with route mapping:
+# route_up_test.t_route -> route_down_test.t_route
+mysql -uroot -h 127.0.0.1 -P 4001 -e "drop database if exists route_up_test;"
+mysql -uroot -h 127.0.0.1 -P 4001 -e "drop database if exists route_down_test;"
+mysql -uroot -h 127.0.0.1 -P 4001 -e "create database route_up_test;"
+mysql -uroot -h 127.0.0.1 -P 4001 -e "create table route_up_test.t_route(id int primary key, val varchar(20));"
+mysql -uroot -h 127.0.0.1 -P 4001 -e "insert into route_up_test.t_route values (1, 'a'), (2, 'b'), (3, 'c'), (4, 'd'), (5, 'e'), (6, 'f'), (7, 'g'), (8, 'h'), (9, 'i'), (10, 'j');"
+
+mysql -uroot -h ${MYSQL_HOST} -P ${MYSQL_PORT} -e "drop database if exists route_down_test;"
+mysql -uroot -h ${MYSQL_HOST} -P ${MYSQL_PORT} -e "create database route_down_test;"
+mysql -uroot -h ${MYSQL_HOST} -P ${MYSQL_PORT} -e "create table route_down_test.t_route(id int primary key, val varchar(20));"
+mysql -uroot -h ${MYSQL_HOST} -P ${MYSQL_PORT} -e "insert into route_down_test.t_route values (1, 'a'), (2, 'b'), (3, 'c'), (4, 'x'), (5, 'e'), (6, 'f'), (7, 'g'), (8, 'h'), (9, 'i'), (10, 'j');"
+
+sed "s/\"127.0.0.1\"#MYSQL_HOST/\"${MYSQL_HOST}\"/g" ./config_base.toml | sed "s/3306#MYSQL_PORT/${MYSQL_PORT}/g" >./config.toml
+
+export GO_FAILPOINTS="main/binsearchSplitThreshold=return(4)"
+sync_diff_inspector --config=./config.toml -L debug >$OUT_DIR/router.output || true
+export GO_FAILPOINTS=""
+
+check_contains "check failed!!!" $OUT_DIR/sync_diff.log
+check_contains "A total of 1 tables have been compared, 0 tables finished, 1 tables failed, 0 tables skipped." $OUT_DIR/router.output
+check_contains "+1/-1" $OUT_DIR/summary.txt
+
+check_contains "get mid by size" $OUT_DIR/sync_diff.log
+grep "get mid by size" $OUT_DIR/sync_diff.log >$OUT_DIR/router_mid.log
+check_contains "FROM \`route_up_test\`.\`t_route\`" $OUT_DIR/router_mid.log
+check_not_contains "FROM \`route_down_test\`.\`t_route\`" $OUT_DIR/router_mid.log