diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/FilterEstimation.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/FilterEstimation.java
index 48bbbea6fbea58b..c36c681706ee4de 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/FilterEstimation.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/FilterEstimation.java
@@ -547,8 +547,8 @@ public Statistics visitIsNull(IsNull isNull, EstimationContext context) {
             Expression child = isNull.child();
             Statistics childStats = child.accept(this, context);
             outputRowCount = Math.max(childStats.getRowCount() * DEFAULT_ISNULL_SELECTIVITY, outputRowCount);
+            outputRowCount = Math.max(outputRowCount, 1);
         }
-        outputRowCount = Math.max(outputRowCount, 1);
 
         ColumnStatisticBuilder colBuilder = new ColumnStatisticBuilder(childColStats);
         colBuilder.setCount(outputRowCount).setNumNulls(outputRowCount)