diff --git a/tests/system-test/2-query/length.py b/tests/system-test/2-query/length.py
index 3dc41ef2e07652e1a666992d3174a0b0833c578a..7f88be9180892de7e68fb41d755a4a1f17ca12d0 100644
--- a/tests/system-test/2-query/length.py
+++ b/tests/system-test/2-query/length.py
@@ -79,9 +79,9 @@ class TDTestCase:
                     if not tdSql.getData(i,1):
                         tdSql.checkData(i, 1, None)
                     elif "as nchar" in condition or (NCHAR_COL in condition and "as binary" not in condition):
-                        tdSql.checkData(i, 1, len(str(tdSql.getData(i,1) ) ) * 4 )
+                        tdSql.checkData(i, 1, len(str(tdSql.getData(i,0) ) ) * 4 )
                     else:
-                        tdSql.checkData(i, 1, len(str(tdSql.getData(i,1) ) ) )
+                        tdSql.checkData(i, 1, len(str(tdSql.getData(i,0) ) ) )
 
 
     def __length_err_check(self,tbname):