diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DateFormat.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DateFormat.java
index 2f5177d23f826b7..1ae130d876d965b 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DateFormat.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DateFormat.java
@@ -53,6 +53,10 @@ public class DateFormat extends ScalarFunction
             FunctionSignature.ret(VarcharType.SYSTEM_DEFAULT).args(DateType.INSTANCE, VarcharType.SYSTEM_DEFAULT)
     );
 
+    private static final Set<String> monoFormat = ImmutableSet.of("yyyyMMdd", "yyyy-MM-dd", "yyyy-MM-dd HH:mm:ss",
+            "%Y", "%Y-%m", "%Y-%m-%d", "%Y-%m-%d%H", "%Y-%m-%d%H:%i", "%Y-%m-%d%H:%i:%s", "%Y-%m-%d%H:%i:%S",
+            "%Y-%m-%d%T", "%Y%m%d", "%Y%m");
+
     /**
      * constructor with 2 arguments.
      */
@@ -86,10 +90,7 @@ public boolean isMonotonic() {
             return false;
         }
         VarcharLiteral varcharLiteral = (VarcharLiteral) format;
-        String str = varcharLiteral.getValue();
-        Set<String> monoFormat = ImmutableSet.of("yyyyMMdd", "yyyy-MM-dd", "yyyy-MM-dd HH:mm:ss", "%Y", "%Y-%m",
-                "%Y-%m-%d", "%Y-%m-%d %H", "%Y-%m-%d %H:%i", "%Y-%m-%d %H:%i:%s", "%Y-%m-%d %H:%i:%S", "%Y-%m-%d %T",
-                "%Y%m%d", "%Y%m");
+        String str = varcharLiteral.getValue().replace(" ", "");
         return monoFormat.contains(str);
     }
 
diff --git a/regression-test/suites/nereids_rules_p0/partition_prune/always_mono_func.groovy b/regression-test/suites/nereids_rules_p0/partition_prune/always_mono_func.groovy
index 722acda8abc1c7e..7fc74d7eb2ac6c1 100644
--- a/regression-test/suites/nereids_rules_p0/partition_prune/always_mono_func.groovy
+++ b/regression-test/suites/nereids_rules_p0/partition_prune/always_mono_func.groovy
@@ -106,7 +106,10 @@ suite("always_mono_func") {
         sql """select * from always_mono_func where date_format(dt, "%Y%m") > "20190101" """
         contains("partitions=2/5 (p4,p5)")
     }
-
+    explain {
+        sql """select * from always_mono_func where date_format(dt, "%Y %m") > "2019 01" """
+        contains("partitions=2/5 (p4,p5)")
+    }
 
     explain {
         sql """ select * from always_mono_func where last_day(dt) > "2019-01-01" """