diff --git a/be/src/vec/functions/function_string.h b/be/src/vec/functions/function_string.h
index 195ef4af76b1d1..c71920c137f98b 100644
--- a/be/src/vec/functions/function_string.h
+++ b/be/src/vec/functions/function_string.h
@@ -3653,9 +3653,10 @@ class FunctionConvertTo : public IFunction {
         auto& res_offset = col_res->get_offsets();
         auto& res_chars = col_res->get_chars();
         res_offset.resize(input_rows_count);
-        // max pinyin size is 6, double of utf8 chinese word 3, add one char to set '~'
-        ColumnString::check_chars_length(str_chars.size() * 2 + input_rows_count, 0);
-        res_chars.resize(str_chars.size() * 2 + input_rows_count);
+        // max pinyin size is 6 + 1 (first '~') for utf8 chinese word 3
+        size_t pinyin_size = (str_chars.size() + 2) / 3 * 7;
+        ColumnString::check_chars_length(pinyin_size, 0);
+        res_chars.resize(pinyin_size);
 
         size_t in_len = 0, out_len = 0;
         for (int i = 0; i < input_rows_count; ++i) {
@@ -3696,7 +3697,11 @@ class FunctionConvertTo : public IFunction {
                     }
 
                     auto end = strchr(buf, ' ');
-                    auto len = end != nullptr ? end - buf : MAX_PINYIN_LEN;
+                    // max len for pinyin is 6
+                    int len = MAX_PINYIN_LEN;
+                    if (end != nullptr && end - buf < MAX_PINYIN_LEN) {
+                        len = end - buf;
+                    }
                     // set first char '~' just make sure all english word lower than chinese word
                     *dest = 126;
                     memcpy(dest + 1, buf, len);
diff --git a/regression-test/data/nereids_function_p0/scalar_function/C.out b/regression-test/data/nereids_function_p0/scalar_function/C.out
index e36fdc7f3742be..924ddf5b148105 100644
--- a/regression-test/data/nereids_function_p0/scalar_function/C.out
+++ b/regression-test/data/nereids_function_p0/scalar_function/C.out
@@ -1418,3 +1418,6 @@ Doris	Doris
 -- !convert --
 1	1
 
+-- !convert_1 --
+~zhuang~zhuang~zhuang~zhuang~zhuang
+
diff --git a/regression-test/data/query_p0/sql_functions/string_functions/test_string_function.out b/regression-test/data/query_p0/sql_functions/string_functions/test_string_function.out
index cadf5039794dd8..4af2997eda286b 100644
Binary files a/regression-test/data/query_p0/sql_functions/string_functions/test_string_function.out and b/regression-test/data/query_p0/sql_functions/string_functions/test_string_function.out differ
diff --git a/regression-test/suites/nereids_function_p0/scalar_function/C.groovy b/regression-test/suites/nereids_function_p0/scalar_function/C.groovy
index bf072c9ad8cf74..0a14602eff9c17 100644
--- a/regression-test/suites/nereids_function_p0/scalar_function/C.groovy
+++ b/regression-test/suites/nereids_function_p0/scalar_function/C.groovy
@@ -197,5 +197,5 @@ suite("nereids_scalar_fn_C") {
 	qt_bitmap_not_nullable "select count(kbitmap) from fn_test_bitmap_not_nullable"
 	qt_char "select char(68, 111, 114, 105, 115), char(68, 111, 114, 105, 115 using utf8);"
 	qt_convert "select convert(1 using gbk), convert(1, string);"
-
+	qt_convert_1 "select convert('装装装装装' using gbk);"
 }
diff --git a/regression-test/suites/query_p0/sql_functions/string_functions/test_string_function.groovy b/regression-test/suites/query_p0/sql_functions/string_functions/test_string_function.groovy
index f5d32653c818b5..b8418a1a318f24 100644
--- a/regression-test/suites/query_p0/sql_functions/string_functions/test_string_function.groovy
+++ b/regression-test/suites/query_p0/sql_functions/string_functions/test_string_function.groovy
@@ -163,6 +163,8 @@ suite("test_string_function") {
     qt_sql "select right(\"Hello doris\", 120);"
     qt_sql "select right(\"Hello doris\", -6);"
 
+    qt_convert_1 "select convert('装装装装装' using gbk);"
+
     sql """ drop table if exists left_right_test; """
     sql """ create table left_right_test (
         id INT NULL,