diff --git a/br/pkg/lightning/backend/kv/BUILD.bazel b/br/pkg/lightning/backend/kv/BUILD.bazel
index e6b75eb3a73f8..1696195d4abe4 100644
--- a/br/pkg/lightning/backend/kv/BUILD.bazel
+++ b/br/pkg/lightning/backend/kv/BUILD.bazel
@@ -53,6 +53,7 @@ go_test(
     embed = [":kv"],
     flaky = True,
     race = "on",
+    shard_count = 19,
     deps = [
         "//br/pkg/lightning/common",
         "//br/pkg/lightning/log",
diff --git a/br/pkg/lightning/backend/kv/sql2kv.go b/br/pkg/lightning/backend/kv/sql2kv.go
index 92d54d723e9d0..1ff8390f6c564 100644
--- a/br/pkg/lightning/backend/kv/sql2kv.go
+++ b/br/pkg/lightning/backend/kv/sql2kv.go
@@ -45,6 +45,10 @@ import (
 	"golang.org/x/exp/slices"
 )
 
+const (
+	maxLogLength = 512 * 1024
+)
+
 var ExtraHandleColumnInfo = model.NewExtraHandleColInfo()
 
 type genCol struct {
@@ -223,6 +227,7 @@ var kindStr = [...]string{
 // MarshalLogArray implements the zapcore.ArrayMarshaler interface
 func (row RowArrayMarshaler) MarshalLogArray(encoder zapcore.ArrayEncoder) error {
 	for _, datum := range row {
+		var totalLength = 0
 		kind := datum.Kind()
 		var str string
 		var err error
@@ -239,6 +244,14 @@ func (row RowArrayMarshaler) MarshalLogArray(encoder zapcore.ArrayEncoder) error
 				return err
 			}
 		}
+		if len(str) > maxLogLength {
+			str = str[0:1024] + " (truncated)"
+		}
+		totalLength += len(str)
+		if totalLength >= maxLogLength {
+			encoder.AppendString("The row has been truncated, and the log has exited early.")
+			return nil
+		}
 		if err := encoder.AppendObject(zapcore.ObjectMarshalerFunc(func(enc zapcore.ObjectEncoder) error {
 			enc.AddString("kind", kindStr[kind])
 			enc.AddString("val", redact.String(str))
@@ -250,7 +263,7 @@ func (row RowArrayMarshaler) MarshalLogArray(encoder zapcore.ArrayEncoder) error
 	return nil
 }
 
-func logKVConvertFailed(logger log.Logger, row []types.Datum, j int, colInfo *model.ColumnInfo, err error) error {
+func LogKVConvertFailed(logger log.Logger, row []types.Datum, j int, colInfo *model.ColumnInfo, err error) error {
 	var original types.Datum
 	if 0 <= j && j < len(row) {
 		original = row[j]
@@ -265,9 +278,16 @@ func logKVConvertFailed(logger log.Logger, row []types.Datum, j int, colInfo *mo
 		log.ShortError(err),
 	)
 
-	logger.Error("failed to convert kv value", logutil.RedactAny("origVal", original.GetValue()),
-		zap.Stringer("fieldType", &colInfo.FieldType), zap.String("column", colInfo.Name.O),
-		zap.Int("columnID", j+1))
+	if len(original.GetString()) >= maxLogLength {
+		originalPrefix := original.GetString()[0:1024] + " (truncated)"
+		logger.Error("failed to convert kv value", logutil.RedactAny("origVal", originalPrefix),
+			zap.Stringer("fieldType", &colInfo.FieldType), zap.String("column", colInfo.Name.O),
+			zap.Int("columnID", j+1))
+	} else {
+		logger.Error("failed to convert kv value", logutil.RedactAny("origVal", original.GetValue()),
+			zap.Stringer("fieldType", &colInfo.FieldType), zap.String("column", colInfo.Name.O),
+			zap.Int("columnID", j+1))
+	}
 	return errors.Annotatef(
 		err,
 		"failed to cast value as %s for column `%s` (#%d)", &colInfo.FieldType, colInfo.Name.O, j+1,
@@ -381,7 +401,7 @@ func (kvcodec *tableKVEncoder) Encode(
 		}
 		value, err = kvcodec.getActualDatum(rowID, i, theDatum)
 		if err != nil {
-			return nil, logKVConvertFailed(logger, row, j, col.ToInfo(), err)
+			return nil, LogKVConvertFailed(logger, row, j, col.ToInfo(), err)
 		}
 
 		record = append(record, value)
@@ -412,7 +432,7 @@ func (kvcodec *tableKVEncoder) Encode(
 			value, err = types.NewIntDatum(rowID), nil
 		}
 		if err != nil {
-			return nil, logKVConvertFailed(logger, row, j, ExtraHandleColumnInfo, err)
+			return nil, LogKVConvertFailed(logger, row, j, ExtraHandleColumnInfo, err)
 		}
 		record = append(record, value)
 		alloc := kvcodec.tbl.Allocators(kvcodec.se).Get(autoid.RowIDAllocType)
diff --git a/br/pkg/lightning/backend/kv/sql2kv_test.go b/br/pkg/lightning/backend/kv/sql2kv_test.go
index c08f63919ef77..d4ab801721921 100644
--- a/br/pkg/lightning/backend/kv/sql2kv_test.go
+++ b/br/pkg/lightning/backend/kv/sql2kv_test.go
@@ -17,7 +17,10 @@ package kv_test
 import (
 	"errors"
 	"fmt"
+	"os"
+	"path/filepath"
 	"reflect"
+	"strings"
 	"testing"
 
 	lkv "github.com/pingcap/tidb/br/pkg/lightning/backend/kv"
@@ -718,3 +721,37 @@ func BenchmarkSQL2KV(b *testing.B) {
 		require.Equal(b, l, 2)
 	}
 }
+
+func TestLogKVConvertFailed(t *testing.T) {
+	tempPath := filepath.Join(t.TempDir(), "/temp.txt")
+	logCfg := &log.Config{File: tempPath, FileMaxSize: 1}
+	err := log.InitLogger(logCfg, "info")
+	require.NoError(t, err)
+
+	modelName := model.NewCIStr("c1")
+	modelState := model.StatePublic
+	modelFieldType := *types.NewFieldType(mysql.TypeTiny)
+	c1 := &model.ColumnInfo{ID: 1, Name: modelName, State: modelState, Offset: 0, FieldType: modelFieldType}
+	cols := []*model.ColumnInfo{c1}
+	tblInfo := &model.TableInfo{ID: 1, Columns: cols, PKIsHandle: false, State: model.StatePublic}
+	_, err = tables.TableFromMeta(lkv.NewPanickingAllocators(0), tblInfo)
+	require.NoError(t, err)
+
+	var newString strings.Builder
+	for i := 0; i < 100000; i++ {
+		newString.WriteString("test_test_test_test_")
+	}
+	newDatum := types.NewStringDatum(newString.String())
+	rows := []types.Datum{}
+	for i := 0; i <= 10; i++ {
+		rows = append(rows, newDatum)
+	}
+	err = lkv.LogKVConvertFailed(log.L(), rows, 6, c1, err)
+	require.NoError(t, err)
+
+	var content []byte
+	content, err = os.ReadFile(tempPath)
+	require.NoError(t, err)
+	require.LessOrEqual(t, 500, len(string(content)))
+	require.NotContains(t, content, "exceeds maximum file size")
+}