diff --git a/fe/fe-core/src/main/java/org/apache/doris/analysis/TypeDef.java b/fe/fe-core/src/main/java/org/apache/doris/analysis/TypeDef.java
index 333047ec01..431e10ce2e 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/analysis/TypeDef.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/analysis/TypeDef.java
@@ -304,9 +304,14 @@ public class TypeDef implements ParseNode {
                 break;
             }
             case DECIMAL256: {
-                SessionVariable sessionVariable = ConnectContext.get().getSessionVariable();
-                boolean enableDecimal256 = sessionVariable.enableDecimal256();
-                boolean enableNereidsPlanner = sessionVariable.isEnableNereidsPlanner();
+                boolean enableNereidsPlanner = false;
+                boolean enableDecimal256 = false;
+                ConnectContext connectContext = ConnectContext.get();
+                if (connectContext != null) {
+                    SessionVariable sessionVariable = connectContext.getSessionVariable();
+                    enableDecimal256 = sessionVariable.enableDecimal256();
+                    enableNereidsPlanner = sessionVariable.isEnableNereidsPlanner();
+                }
                 if (enableNereidsPlanner && enableDecimal256) {
                     int precision = scalarType.decimalPrecision();
                     int scale = scalarType.decimalScale();
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Multiply.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Multiply.java
index ebf984362b..c420e061a5 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Multiply.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Multiply.java
@@ -53,7 +53,11 @@ public class Multiply extends BinaryArithmetic implements CheckOverflowNullable
         int retPercision = t1.getPrecision() + t2.getPrecision();
         int retScale = t1.getScale() + t2.getScale();
         if (retPercision > DecimalV3Type.MAX_DECIMAL128_PRECISION) {
-            boolean enableDecimal256 = ConnectContext.get().getSessionVariable().enableDecimal256();
+            boolean enableDecimal256 = false;
+            ConnectContext connectContext = ConnectContext.get();
+            if (connectContext != null) {
+                enableDecimal256 = connectContext.getSessionVariable().enableDecimal256();
+            }
             if (enableDecimal256) {
                 if (retPercision > DecimalV3Type.MAX_DECIMAL256_PRECISION) {
                     retPercision = DecimalV3Type.MAX_DECIMAL256_PRECISION;
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/ComputePrecisionForSum.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/ComputePrecisionForSum.java
index 7480c510ba..d78567e165 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/ComputePrecisionForSum.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/ComputePrecisionForSum.java
@@ -29,7 +29,11 @@ public interface ComputePrecisionForSum extends ComputePrecision {
         DataType argumentType = getArgumentType(0);
         if (signature.getArgType(0) instanceof DecimalV3Type) {
             DecimalV3Type decimalV3Type = DecimalV3Type.forType(argumentType);
-            boolean enableDecimal256 = ConnectContext.get().getSessionVariable().enableDecimal256();
+            boolean enableDecimal256 = false;
+            ConnectContext connectContext = ConnectContext.get();
+            if (connectContext != null) {
+                enableDecimal256 = connectContext.getSessionVariable().enableDecimal256();
+            }
             return signature.withArgumentType(0, decimalV3Type)
                     .withReturnType(DecimalV3Type.createDecimalV3Type(
                             enableDecimal256 ? DecimalV3Type.MAX_DECIMAL256_PRECISION
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/agg/Avg.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/agg/Avg.java
index cc75c5767c..9586348486 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/agg/Avg.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/agg/Avg.java
@@ -89,7 +89,11 @@ public class Avg extends NullableAggregateFunction
     public FunctionSignature computePrecision(FunctionSignature signature) {
         DataType argumentType = getArgumentType(0);
         if (signature.getArgType(0) instanceof DecimalV3Type) {
-            boolean enableDecimal256 = ConnectContext.get().getSessionVariable().enableDecimal256();
+            boolean enableDecimal256 = false;
+            ConnectContext connectContext = ConnectContext.get();
+            if (connectContext != null) {
+                enableDecimal256 = connectContext.getSessionVariable().enableDecimal256();
+            }
             DecimalV3Type decimalV3Type = DecimalV3Type.forType(argumentType);
             // DecimalV3 scale lower than DEFAULT_MIN_AVG_DECIMAL128_SCALE should do cast
             int precision = decimalV3Type.getPrecision();
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/types/DecimalV3Type.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/types/DecimalV3Type.java
index 7aa3da9470..6d1e43383b 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/types/DecimalV3Type.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/types/DecimalV3Type.java
@@ -107,7 +107,11 @@ public class DecimalV3Type extends FractionalType {
         Preconditions.checkArgument(scale >= 0, "scale should not smaller than 0, but real scale is " + scale);
         Preconditions.checkArgument(precision >= scale, "precision should not smaller than scale,"
                 + " but precision is " + precision, ", scale is " + scale);
-        boolean enableDecimal256 = ConnectContext.get().getSessionVariable().enableDecimal256();
+        boolean enableDecimal256 = false;
+        ConnectContext connectContext = ConnectContext.get();
+        if (connectContext != null) {
+            enableDecimal256 = connectContext.getSessionVariable().enableDecimal256();
+        }
         if (precision > MAX_DECIMAL128_PRECISION && !enableDecimal256) {
             throw new NotSupportedException("Datatype DecimalV3 with precision " + precision
                     + ", which is greater than 38 is disabled by default. set enable_decimal256 = true to enable it.");
@@ -126,7 +130,11 @@ public class DecimalV3Type extends FractionalType {
      * create DecimalV3Type, not throwing NotSupportedException.
      */
     public static DecimalV3Type createDecimalV3TypeLooseCheck(int precision, int scale) {
-        boolean enableDecimal256 = ConnectContext.get().getSessionVariable().enableDecimal256();
+        boolean enableDecimal256 = false;
+        ConnectContext connectContext = ConnectContext.get();
+        if (connectContext != null) {
+            enableDecimal256 = connectContext.getSessionVariable().enableDecimal256();
+        }
         if (enableDecimal256) {
             Preconditions.checkArgument(precision > 0 && precision <= MAX_DECIMAL256_PRECISION,
                     "precision should in (0, " + MAX_DECIMAL256_PRECISION + "], but real precision is " + precision);
@@ -158,7 +166,11 @@ public class DecimalV3Type extends FractionalType {
             boolean overflowToDouble) {
         int scale = Math.max(leftScale, rightScale);
         int range = Math.max(leftPrecision - leftScale, rightPrecision - rightScale);
-        boolean enableDecimal256 = ConnectContext.get().getSessionVariable().enableDecimal256();
+        boolean enableDecimal256 = false;
+        ConnectContext connectContext = ConnectContext.get();
+        if (connectContext != null) {
+            enableDecimal256 = connectContext.getSessionVariable().enableDecimal256();
+        }
         if (range + scale > (enableDecimal256 ? MAX_DECIMAL256_PRECISION : MAX_DECIMAL128_PRECISION)
                 && overflowToDouble) {
             return DoubleType.INSTANCE;
@@ -232,7 +244,11 @@ public class DecimalV3Type extends FractionalType {
         } else if (precision <= MAX_DECIMAL128_PRECISION) {
             return 16;
         } else {
-            boolean enableDecimal256 = ConnectContext.get().getSessionVariable().enableDecimal256();
+            boolean enableDecimal256 = false;
+            ConnectContext connectContext = ConnectContext.get();
+            if (connectContext != null) {
+                enableDecimal256 = connectContext.getSessionVariable().enableDecimal256();
+            }
             if (enableDecimal256) {
                 return 32;
             } else {
diff --git a/fe/fe-core/src/test/java/org/apache/doris/catalog/ColumnTypeTest.java b/fe/fe-core/src/test/java/org/apache/doris/catalog/ColumnTypeTest.java
index 351a0e9b3e..87503b3a84 100644
--- a/fe/fe-core/src/test/java/org/apache/doris/catalog/ColumnTypeTest.java
+++ b/fe/fe-core/src/test/java/org/apache/doris/catalog/ColumnTypeTest.java
@@ -189,7 +189,7 @@ public class ColumnTypeTest {
     public void testDecimalPreFail() throws AnalysisException {
         TypeDef type;
         if (Config.enable_decimal_conversion) {
-            type = TypeDef.createDecimal(39, 3);
+            type = TypeDef.createDecimal(77, 3);
         } else {
             type = TypeDef.createDecimal(28, 3);
         }