diff --git a/src/main/java/org/bdware/server/trustedmodel/SelfAdaptiveShardingExecutor.java b/src/main/java/org/bdware/server/trustedmodel/SelfAdaptiveShardingExecutor.java
index ca82728..d5a03bb 100644
--- a/src/main/java/org/bdware/server/trustedmodel/SelfAdaptiveShardingExecutor.java
+++ b/src/main/java/org/bdware/server/trustedmodel/SelfAdaptiveShardingExecutor.java
@@ -13,10 +13,7 @@ import org.bdware.sc.util.JsonUtil;
 import org.bdware.server.action.p2p.MasterServerRecoverMechAction;
 import org.bdware.server.action.p2p.MasterServerTCPAction;
 
-import java.util.Arrays;
-import java.util.Map;
-import java.util.Queue;
-import java.util.Set;
+import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.ScheduledFuture;
@@ -97,7 +94,9 @@ public class SelfAdaptiveShardingExecutor implements ContractExecutor {
                 block.prevHash,
                 block.requests.length,
                 block.timestamp));
-        if (!executedBlocks.contains(block.hash)) {
+        if (!toExecuted.containsKey(block.prevHash) &&
+                !executedBlocks.contains(block.hash) &&
+                block.isValid()) {
             toExecuted.put(block.prevHash, block);
             synchronized (flag) {
                 flag.notify();
@@ -149,7 +148,7 @@ public class SelfAdaptiveShardingExecutor implements ContractExecutor {
         for (int i = 0; i < requests.length; ++i) {
             requests[i] = reqQueue.poll();
         }
-        this.b.fillBlock(null, requests);
+        this.b.fillBlock(requests);
         return this.b;
     }
 
@@ -157,6 +156,7 @@ public class SelfAdaptiveShardingExecutor implements ContractExecutor {
         String prevHash = "0";
         String hash;
         String checkPoint;
+        String body;
         ContractRequest[] requests;
         long timestamp;
 
@@ -167,14 +167,46 @@ public class SelfAdaptiveShardingExecutor implements ContractExecutor {
             this.prevHash = prev;
         }
 
-        public void fillBlock(String cp, ContractRequest[] requests) {
-            this.checkPoint = cp;
+        public void fillBlock(ContractRequest[] requests) {
             this.requests = requests;
             this.timestamp = System.currentTimeMillis();
-            hash = HashUtil.sha3(
-                    prevHash,
-                    cp,
-                    Arrays.stream(requests).map(ContractRequest::getRequestID).collect(Collectors.joining()));
+            this.body = merkle(requests);
+            this.hash = computeHash();
         }
+
+        public boolean isValid() {
+            return computeHash().equals(hash) && body.equals(merkle(this.requests));
+        }
+
+        private String computeHash() {
+            return HashUtil.sha3(
+                    this.prevHash,
+                    this.checkPoint,
+                    this.body);
+        }
+
+
+        private String merkle(ContractRequest[] requests) {
+            if (requests.length == 0) {
+                return null;
+            }
+            if (requests.length == 1) {
+                return HashUtil.sha3(requests[0].getRequestID());
+            }
+            Queue<String> reqQueue =
+                    Arrays.stream(requests).map(ContractRequest::getRequestID)
+                            .collect(Collectors.toCollection(ArrayDeque::new));
+            do {
+                int size;
+                for (size = reqQueue.size(); size > 1; size -= 2) {
+                    reqQueue.add(HashUtil.sha3(reqQueue.poll(), reqQueue.poll()));
+                }
+                if (size == 1) {
+                    reqQueue.add(reqQueue.poll());
+                }
+            } while (1 != reqQueue.size());
+            return reqQueue.poll();
+        }
+
     }
 }