diff --git a/expression/builtin_string.go b/expression/builtin_string.go
index b8882bbcf4080..5d942effe78d3 100644
--- a/expression/builtin_string.go
+++ b/expression/builtin_string.go
@@ -2696,8 +2696,11 @@ func (b *builtinQuoteSig) Clone() builtinFunc {
 // See https://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_quote
 func (b *builtinQuoteSig) evalString(row chunk.Row) (string, bool, error) {
 	str, isNull, err := b.args[0].EvalString(b.ctx, row)
-	if isNull || err != nil {
+	if err != nil {
 		return "", true, err
+	} else if isNull {
+		// If the argument is NULL, the return value is the word "NULL" without enclosing single quotation marks. see ref.
+		return "NULL", false, err
 	}
 
 	runes := []rune(str)
diff --git a/expression/builtin_string_test.go b/expression/builtin_string_test.go
index b07ebd7d11f13..0272e2b7d8c20 100644
--- a/expression/builtin_string_test.go
+++ b/expression/builtin_string_test.go
@@ -2168,7 +2168,7 @@ func (s *testEvaluatorSuite) TestQuote(c *C) {
 		{`萌萌哒(๑•ᴗ•๑)😊`, `'萌萌哒(๑•ᴗ•๑)😊'`},
 		{`㍿㌍㍑㌫`, `'㍿㌍㍑㌫'`},
 		{string([]byte{0, 26}), `'\0\Z'`},
-		{nil, nil},
+		{nil, "NULL"},
 	}
 
 	for _, t := range tbl {
diff --git a/expression/integration_test.go b/expression/integration_test.go
index 27ea98a6bc7ff..7fbaaa7494b51 100644
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -900,7 +900,14 @@ func (s *testIntegrationSuite) TestStringBuiltin(c *C) {
 	result = tk.MustQuery(`select quote("aaaa"), quote(""), quote("\"\""), quote("\n\n");`)
 	result.Check(testkit.Rows("'aaaa' '' '\"\"' '\n\n'"))
 	result = tk.MustQuery(`select quote(0121), quote(0000), quote("中文"), quote(NULL);`)
-	result.Check(testkit.Rows("'121' '0' '中文' <nil>"))
+	result.Check(testkit.Rows("'121' '0' '中文' NULL"))
+	tk.MustQuery(`select quote(null) is NULL;`).Check(testkit.Rows(`0`))
+	tk.MustQuery(`select quote(null) is NOT NULL;`).Check(testkit.Rows(`1`))
+	tk.MustQuery(`select length(quote(null));`).Check(testkit.Rows(`4`))
+	tk.MustQuery(`select quote(null) REGEXP binary 'null'`).Check(testkit.Rows(`0`))
+	tk.MustQuery(`select quote(null) REGEXP binary 'NULL'`).Check(testkit.Rows(`1`))
+	tk.MustQuery(`select quote(null) REGEXP 'NULL'`).Check(testkit.Rows(`1`))
+	tk.MustQuery(`select quote(null) REGEXP 'null'`).Check(testkit.Rows(`1`))
 
 	// for convert
 	result = tk.MustQuery(`select convert("123" using "binary"), convert("中文" using "binary"), convert("中文" using "utf8"), convert("中文" using "utf8mb4"), convert(cast("中文" as binary) using "utf8");`)