diff --git a/br/pkg/backup/client.go b/br/pkg/backup/client.go
index 07bfd3aa4c253..b675b062793c6 100644
--- a/br/pkg/backup/client.go
+++ b/br/pkg/backup/client.go
@@ -180,14 +180,9 @@ func (bc *Client) SetStorage(ctx context.Context, backend *backuppb.StorageBacke
 			"there may be some backup files in the path already, "+
 			"please specify a correct backup directory!", bc.storage.URI()+"/"+metautil.MetaFile)
 	}
-	exist, err = bc.storage.FileExists(ctx, metautil.LockFile)
+	err = CheckBackupStorageIsLocked(ctx, bc.storage)
 	if err != nil {
-		return errors.Annotatef(err, "error occurred when checking %s file", metautil.LockFile)
-	}
-	if exist {
-		return errors.Annotatef(berrors.ErrInvalidArgument, "backup lock file exists in %v, "+
-			"there may be some backup files in the path already, "+
-			"please specify a correct backup directory!", bc.storage.URI()+"/"+metautil.LockFile)
+		return err
 	}
 	bc.backend = backend
 	return nil
@@ -198,6 +193,29 @@ func (bc *Client) GetClusterID() uint64 {
 	return bc.clusterID
 }
 
+// CheckBackupStorageIsLocked checks whether backups is locked.
+// which means we found other backup progress already write
+// some data files into the same backup directory or cloud prefix.
+func CheckBackupStorageIsLocked(ctx context.Context, s storage.ExternalStorage) error {
+	exist, err := s.FileExists(ctx, metautil.LockFile)
+	if err != nil {
+		return errors.Annotatef(err, "error occurred when checking %s file", metautil.LockFile)
+	}
+	if exist {
+		err = s.WalkDir(ctx, &storage.WalkOption{}, func(path string, size int64) error {
+			// should return error to break the walkDir when found lock file and other .sst files.
+			if strings.HasSuffix(path, ".sst") {
+				return errors.Annotatef(berrors.ErrInvalidArgument, "backup lock file and sst file exist in %v, "+
+					"there are some backup files in the path already, "+
+					"please specify a correct backup directory!", s.URI()+"/"+metautil.LockFile)
+			}
+			return nil
+		})
+		return err
+	}
+	return nil
+}
+
 // BuildTableRanges returns the key ranges encompassing the entire table,
 // and its partitions if exists.
 func BuildTableRanges(tbl *model.TableInfo) ([]kv.KeyRange, error) {
diff --git a/br/pkg/backup/client_test.go b/br/pkg/backup/client_test.go
index 3c3688f79bc9f..e46d832bae3ee 100644
--- a/br/pkg/backup/client_test.go
+++ b/br/pkg/backup/client_test.go
@@ -70,6 +70,13 @@ func (r *testBackup) SetUpSuite(c *C) {
 
 }
 
+func (r *testBackup) resetStorage(c *C) {
+	var err error
+	base := c.MkDir()
+	r.storage, err = storage.NewLocalStorage(base)
+	c.Assert(err, IsNil)
+}
+
 func (r *testBackup) TestGetTS(c *C) {
 	var (
 		err error
@@ -335,3 +342,30 @@ func (r *testBackup) TestskipUnsupportedDDLJob(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(len(allDDLJobs), Equals, 8)
 }
+
+func (r *testBackup) TestCheckBackupIsLocked(c *C) {
+	ctx := context.Background()
+
+	r.resetStorage(c)
+	// check passed with an empty storage
+	err := backup.CheckBackupStorageIsLocked(ctx, r.storage)
+	c.Assert(err, IsNil)
+
+	// check passed with only a lock file
+	err = r.storage.WriteFile(ctx, metautil.LockFile, nil)
+	c.Assert(err, IsNil)
+	err = backup.CheckBackupStorageIsLocked(ctx, r.storage)
+	c.Assert(err, IsNil)
+
+	// check passed with a lock file and other non-sst files.
+	err = r.storage.WriteFile(ctx, "1.txt", nil)
+	c.Assert(err, IsNil)
+	err = backup.CheckBackupStorageIsLocked(ctx, r.storage)
+	c.Assert(err, IsNil)
+
+	// check failed
+	err = r.storage.WriteFile(ctx, "1.sst", nil)
+	c.Assert(err, IsNil)
+	err = backup.CheckBackupStorageIsLocked(ctx, r.storage)
+	c.Assert(err, ErrorMatches, "backup lock file and sst file exist in(.+)")
+}