diff --git a/plugins/input/kafka/input_kafka.go b/plugins/input/kafka/input_kafka.go
index 5d5cf37cc0..e80775c477 100644
--- a/plugins/input/kafka/input_kafka.go
+++ b/plugins/input/kafka/input_kafka.go
@@ -23,6 +23,7 @@ import (
 	"github.com/IBM/sarama"
 
 	"github.com/alibaba/ilogtail/pkg/logger"
+	"github.com/alibaba/ilogtail/pkg/models"
 	"github.com/alibaba/ilogtail/pkg/pipeline"
 	"github.com/alibaba/ilogtail/pkg/pipeline/extensions"
 	"github.com/alibaba/ilogtail/pkg/protocol/decoder"
@@ -239,7 +240,11 @@ func (k *InputKafka) onMessage(msg *sarama.ConsumerMessage) {
 		switch k.version {
 		case v1:
 			fields := make(map[string]string)
-			fields[string(msg.Key)] = string(msg.Value)
+			if len(msg.Key) == 0 {
+				fields[models.ContentKey] = string(msg.Value)
+			} else {
+				fields[string(msg.Key)] = string(msg.Value)
+			}
 			k.collectorV1.AddData(nil, fields)
 		case v2:
 			data, err := k.decoder.DecodeV2(msg.Value, nil)