diff --git a/utils/sync/src/main/java/com/lanyuanxiaoyao/service/sync/functions/type/TypeConverterV2.java b/utils/sync/src/main/java/com/lanyuanxiaoyao/service/sync/functions/type/TypeConverterV2.java
index 8ece80b..17ee518 100644
--- a/utils/sync/src/main/java/com/lanyuanxiaoyao/service/sync/functions/type/TypeConverterV2.java
+++ b/utils/sync/src/main/java/com/lanyuanxiaoyao/service/sync/functions/type/TypeConverterV2.java
@@ -136,41 +136,23 @@ public class TypeConverterV2 implements TypeConverter {
 
     private Object covertValue(Schema schema, String name, Object value) {
         try {
-            if (ObjectUtil.isNull(value)) {
-                return value;
+            if (isNullValue(value)) {
+                return null;
             } else if (NULLABLE_BOOLEAN_SCHEMA.equals(schema) || BOOLEAN_SCHEMA.equals(schema)) {
-                if (isNullValue(value)) {
-                    return null;
-                }
                 return value instanceof String ? Boolean.valueOf((String) value) : value;
             } else if (NULLABLE_INT_SCHEMA.equals(schema) || INT_SCHEMA.equals(schema)) {
-                if (isNullValue(value)) {
-                    return null;
-                }
                 return value instanceof String ? Integer.valueOf((String) value) : value;
             } else if (NULLABLE_LONG_SCHEMA.equals(schema) || LONG_SCHEMA.equals(schema)) {
-                if (isNullValue(value)) {
-                    return null;
-                }
                 return value instanceof String ? Long.valueOf((String) value) : value;
             } else if (NULLABLE_FLOAT_SCHEMA.equals(schema) || FLOAT_SCHEMA.equals(schema)) {
-                if (isNullValue(value)) {
-                    return null;
-                }
                 return value instanceof String ? Float.valueOf((String) value) : value;
             } else if (NULLABLE_DOUBLE_SCHEMA.equals(schema) || DOUBLE_SCHEMA.equals(schema)) {
-                if (isNullValue(value)) {
-                    return null;
-                }
                 return value instanceof String ? Double.valueOf((String) value) : value;
             } else if (NULLABLE_STRING_SCHEMA.equals(schema) || STRING_SCHEMA.equals(schema)) {
                 return StringData.fromString((String) value);
             } else {
                 for (Schema type : schema.getTypes()) {
                     if (type.getLogicalType() instanceof LogicalTypes.Decimal) {
-                        if (isNullValue(value)) {
-                            return null;
-                        }
                         LogicalTypes.Decimal decimalType = (LogicalTypes.Decimal) type.getLogicalType();
                         int precision = decimalType.getPrecision();
                         int scala = decimalType.getScale();
@@ -188,6 +170,6 @@ public class TypeConverterV2 implements TypeConverter {
     }
 
     private boolean isNullValue(Object value) {
-        return StrUtil.isBlankIfStr(value) || (value instanceof String ? "null".equalsIgnoreCase((String) value) : value == null);
+        return ObjectUtil.isNull(value) || StrUtil.isBlankIfStr(value) || (value instanceof String && StrUtil.equalsAny((String) value, "null", "NULL"));
     }
 }
diff --git a/utils/sync/src/test/java/com/lanyuanxiaoyao/service/sync/TypeConvertTest.java b/utils/sync/src/test/java/com/lanyuanxiaoyao/service/sync/TypeConvertTest.java
index d955302..2cbcaf5 100644
--- a/utils/sync/src/test/java/com/lanyuanxiaoyao/service/sync/TypeConvertTest.java
+++ b/utils/sync/src/test/java/com/lanyuanxiaoyao/service/sync/TypeConvertTest.java
@@ -10,8 +10,15 @@ import org.apache.hudi.org.apache.avro.Schema;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
-import static com.lanyuanxiaoyao.service.sync.functions.type.TypeConverterV2.*;
+import static com.lanyuanxiaoyao.service.sync.functions.type.TypeConverterV2.NULLABLE_BOOLEAN_SCHEMA;
+import static com.lanyuanxiaoyao.service.sync.functions.type.TypeConverterV2.NULLABLE_DECIMAL_SCHEMA;
+import static com.lanyuanxiaoyao.service.sync.functions.type.TypeConverterV2.NULLABLE_DOUBLE_SCHEMA;
+import static com.lanyuanxiaoyao.service.sync.functions.type.TypeConverterV2.NULLABLE_FLOAT_SCHEMA;
+import static com.lanyuanxiaoyao.service.sync.functions.type.TypeConverterV2.NULLABLE_INT_SCHEMA;
+import static com.lanyuanxiaoyao.service.sync.functions.type.TypeConverterV2.NULLABLE_LONG_SCHEMA;
+import static com.lanyuanxiaoyao.service.sync.functions.type.TypeConverterV2.NULLABLE_STRING_SCHEMA;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 
 /**
@@ -91,6 +98,11 @@ public class TypeConvertTest {
 
         // null
         assertNull(convertValue.exec(NULLABLE_BOOLEAN_SCHEMA, "test", null));
+        assertNull(convertValue.exec(NULLABLE_STRING_SCHEMA, "test", "null"));
+        assertNull(convertValue.exec(NULLABLE_STRING_SCHEMA, "test", "NULL"));
+        assertNull(convertValue.exec(NULLABLE_STRING_SCHEMA, "test", null));
+        assertNull(convertValue.exec(NULLABLE_STRING_SCHEMA, "test", ""));
+        assertNotNull(convertValue.exec(NULLABLE_STRING_SCHEMA, "test", "Null"));
 
         // boolean
         assertEquals(true, convertValue.exec(NULLABLE_BOOLEAN_SCHEMA, "test", "true"));