diff --git a/fe/fe-core/src/main/java/org/apache/doris/analysis/Expr.java b/fe/fe-core/src/main/java/org/apache/doris/analysis/Expr.java
index f27a3f107f1961..17a74055b99ba2 100755
--- a/fe/fe-core/src/main/java/org/apache/doris/analysis/Expr.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/analysis/Expr.java
@@ -34,6 +34,7 @@
 import com.google.common.base.MoreObjects;
 import com.google.common.base.Objects;
 import com.google.common.base.Preconditions;
+import com.google.common.base.Strings;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 
@@ -470,7 +471,7 @@ public static String debugString(List<? extends Expr> exprs) {
         }
         List<String> strings = Lists.newArrayList();
         for (Expr expr : exprs) {
-            strings.add(expr.debugString());
+            strings.add(Strings.nullToEmpty(expr.debugString()));
         }
         return "(" + Joiner.on(" ").join(strings) + ")";
     }