diff --git a/sync_diff_inspector/diff.go b/sync_diff_inspector/diff.go
index 94b95d58..b46885d0 100644
--- a/sync_diff_inspector/diff.go
+++ b/sync_diff_inspector/diff.go
@@ -322,6 +322,28 @@ func (df *Diff) compareStruct(ctx context.Context, tableIndex int) (isEqual bool
 	return isEqual, isSkip, nil
 }
 
+func GetSnapshot(latestSnap []string, snap string, db *sql.DB) string {
+	if len(latestSnap) != 1 {
+		return snap
+	}
+
+	latestSnapshotVal, err := utils.ParseSnapshotToTSO(db, latestSnap[0])
+	if err != nil || latestSnapshotVal == 0 {
+		return snap
+	}
+
+	snapshotVal, err := utils.ParseSnapshotToTSO(db, snap)
+	if err != nil {
+		return latestSnap[0]
+	}
+
+	// compare the snapshot and choose the small one to lock
+	if latestSnapshotVal < snapshotVal {
+		return latestSnap[0]
+	}
+	return snap
+}
+
 func (df *Diff) startGCKeeperForTiDB(ctx context.Context, db *sql.DB, snap string) {
 	pdCli, _ := utils.GetPDClientForGC(ctx, db)
 	if pdCli != nil {
@@ -332,15 +354,7 @@ func (df *Diff) startGCKeeperForTiDB(ctx context.Context, db *sql.DB, snap strin
 			return
 		}
 
-		if len(latestSnap) == 1 {
-			if len(snap) == 0 {
-				snap = latestSnap[0]
-			}
-			// compare the snapshot and choose the small one to lock
-			if strings.Compare(latestSnap[0], snap) < 0 {
-				snap = latestSnap[0]
-			}
-		}
+		snap = GetSnapshot(latestSnap, snap, db)
 
 		err = utils.StartGCSavepointUpdateService(ctx, pdCli, db, snap)
 		if err != nil {
diff --git a/sync_diff_inspector/diff_test.go b/sync_diff_inspector/diff_test.go
new file mode 100644
index 00000000..193dbe2c
--- /dev/null
+++ b/sync_diff_inspector/diff_test.go
@@ -0,0 +1,107 @@
+// Copyright 2024 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetSnapshot(t *testing.T) {
+	cases := []struct {
+		latestSnapshot []string
+		snapshot       string
+		expected       string
+		snapshotRows   string
+	}{
+		{
+			latestSnapshot: []string{},
+			snapshot:       "1",
+			expected:       "1",
+		},
+		{
+			latestSnapshot: []string{"2"},
+			snapshot:       "",
+			expected:       "2",
+		},
+		{
+			latestSnapshot: []string{"0"},
+			snapshot:       "3",
+			expected:       "3",
+		},
+		{
+			latestSnapshot: []string{"4"},
+			snapshot:       "0",
+			expected:       "0",
+		},
+		{
+			latestSnapshot: []string{"5"},
+			snapshot:       "6",
+			expected:       "5",
+		},
+		{
+			latestSnapshot: []string{"7"},
+			snapshot:       "6",
+			expected:       "6",
+		},
+		{
+			// 2017-10-07 16:45:26
+			latestSnapshot: []string{"395146933305344000"},
+			snapshot:       "2017-10-08 16:45:26",
+			expected:       "395146933305344000",
+			snapshotRows:   "1507452326",
+		},
+		{
+			// 2017-10-07 16:45:26
+			latestSnapshot: []string{"395146933305344000"},
+			snapshot:       "2017-10-06 16:45:26",
+			expected:       "2017-10-06 16:45:26",
+			snapshotRows:   "1507279526",
+		},
+		{
+			latestSnapshot: []string{"1"},
+			snapshot:       "2017-10-06 16:45:26",
+			expected:       "1",
+			snapshotRows:   "1507279526",
+		},
+		{
+			latestSnapshot: []string{"395146933305344000"},
+			snapshot:       "1",
+			expected:       "1",
+		},
+		{
+			// 2090-11-19 22:07:45
+			latestSnapshot: []string{"1000022649077760000"},
+			snapshot:       "2090-11-18 22:07:45",
+			expected:       "2090-11-18 22:07:45",
+			snapshotRows:   "3814697265",
+		},
+	}
+
+	conn, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer conn.Close()
+
+	for i, cs := range cases {
+		if len(cs.snapshotRows) > 0 {
+			dataRows := sqlmock.NewRows([]string{""}).AddRow(cs.snapshotRows)
+			mock.ExpectQuery("SELECT unix_timestamp(?)").WillReturnRows(dataRows)
+		}
+		val := GetSnapshot(cs.latestSnapshot, cs.snapshot, conn)
+		require.Equal(t, cs.expected, val, "case %d", i)
+	}
+
+}
diff --git a/sync_diff_inspector/utils/pd.go b/sync_diff_inspector/utils/pd.go
index e3c92f16..4f7db4e8 100644
--- a/sync_diff_inspector/utils/pd.go
+++ b/sync_diff_inspector/utils/pd.go
@@ -207,7 +207,7 @@ func StartGCSavepointUpdateService(ctx context.Context, pdCli pd.Client, db *sql
 		return nil
 	}
 	// get latest snapshot
-	snapshotTS, err := parseSnapshotToTSO(db, snapshot)
+	snapshotTS, err := ParseSnapshotToTSO(db, snapshot)
 	if tidbVersion.Compare(*autoGCSafePointVersion) > 0 {
 		log.Info("tidb support auto gc safepoint", zap.Stringer("version", tidbVersion))
 		if err != nil {
@@ -249,7 +249,7 @@ func updateServiceSafePoint(ctx context.Context, pdClient pd.Client, snapshotTS
 	}
 }
 
-func parseSnapshotToTSO(pool *sql.DB, snapshot string) (uint64, error) {
+func ParseSnapshotToTSO(pool *sql.DB, snapshot string) (uint64, error) {
 	snapshotTS, err := strconv.ParseUint(snapshot, 10, 64)
 	if err == nil {
 		return snapshotTS, nil