diff --git a/node/mempool.js b/node/mempool.js
index 84122b45..b5c34df9 100644
--- a/node/mempool.js
+++ b/node/mempool.js
@@ -2,19 +2,22 @@
 
 const typeforce = require('typeforce');
 const debugLib = require('debug');
-const { sleep } = require('../utils');
+const {sleep} = require('../utils');
 const types = require('../types');
 const Tick = require('tick-tock');
+const {Dag} = require('dagjs');
 
 const debug = debugLib('mempool:');
 
 // TODO: add tx expiration (14 days?)
 
-module.exports = ({ Constants, Transaction }) =>
+module.exports = ({Constants, Transaction}) =>
     class Mempool {
         constructor(options) {
             this._mapTxns = new Map();
             this._tock = new Tick(this);
+            this._dag = new Dag();
+            this._dag.testForCyclic = false;
             this._tock.setInterval('outdatedTimer', this.purgeOutdated.bind(this), Constants.MEMPOOL_OUTDATED_INTERVAL);
 
         }
@@ -35,6 +38,7 @@ module.exports = ({ Constants, Transaction }) =>
                 // TODO: think about: is it problem that TX isn't present in mempool, but present in block
                 if (this._mapTxns.has(txHash)) {
                     this._mapTxns.delete(txHash);
+                    this._dag.removeVertex(txHash);
                 } else {
                     debug(`removeTxns: no TX ${txHash} in mempool`);
                 }
@@ -45,6 +49,7 @@ module.exports = ({ Constants, Transaction }) =>
             this._mapTxns.forEach((tx, hash) => {
                 if (tx.arrived < Date.now() - Constants.MEMPOOL_TX_LIFETIME) {
                     this._mapTxns.delete(hash);
+                    this._dag.removeVertex(hash);
                 }
             })
         }
@@ -54,6 +59,7 @@ module.exports = ({ Constants, Transaction }) =>
             let i = Math.floor(this._mapTxns.size / 3);
             for (let [hash, tx] of this._mapTxns) {
                 this._mapTxns.delete(hash);
+                this._dag.removeVertex(hash);
                 if (--i == 0) break;
             }
         }
@@ -77,7 +83,10 @@ module.exports = ({ Constants, Transaction }) =>
             const strHash = tx.hash();
             if (this._mapTxns.has(strHash)) throw new Error(`tx ${strHash} already in mempool`);
 
-            this._mapTxns.set(strHash, { tx, arrived: Date.now() });
+            this._mapTxns.set(strHash, {tx, arrived: Date.now()});
+            for (const input of tx.inputs) {
+                this._dag.add(input.txHash.toString('hex'), strHash);
+            }
             debug(`TX ${strHash} added`);
         }
 
@@ -107,9 +116,40 @@ module.exports = ({ Constants, Transaction }) =>
             // TODO: implement lock_time
             // TODO: implement cache if mempool becomes huge
             const arrResult = [];
-            for (let r of this._mapTxns.values()) {
-                if (r.tx.witnessGroupId === groupId) arrResult.push(r.tx);
+            for (let hash of this._sortTxns()){
+                const r = this._mapTxns.get(hash);
+                if (r.tx.witnessGroupId == groupId) arrResult.push(r.tx);
             }
             return arrResult;
         }
+
+        /**
+         * 
+         * @returns sorted tx hashes array
+         */
+        _sortTxns() {
+            let level = [];
+            let used = [...this._dag.tips];
+            let notused = [...this._mapTxns.keys()];
+            while (notused.length > 0) {
+              level[level.length] = new Array();
+              for (let i = 0; i < notused.length; i++) {
+                const v = notused[i]
+                let k = 0;
+                const edgesTo = this._dag._edges.get(v);
+                if (edgesTo) { 
+                  k = edgesTo.length;
+                  const fromPrevLevel = edgesTo.filter(e => ~used.indexOf(e.from));
+                  if(fromPrevLevel) k -= fromPrevLevel.length
+                }
+                if (k == 0) {
+                  level[level.length - 1].push(v)
+                  notused.splice(i, 1);
+                  i--;
+                }
+              }
+              used.push(...level[level.length - 1])
+            }
+            return [].concat(...level);
+        }
     };
diff --git a/tests/mempool.spec.js b/tests/mempool.spec.js
index ef5226ac..ebf223cd 100644
--- a/tests/mempool.spec.js
+++ b/tests/mempool.spec.js
@@ -31,6 +31,7 @@ describe('Mempool tests', () => {
 
         mempool.addTx(tx);
         assert.isOk(mempool.hasTx(tx.hash()));
+        assert.isOk(mempool._dag.hasVertex(tx.hash()))
     });
 
     it('should FAIL add tx to mempool (already exists)', async () => {
@@ -82,6 +83,9 @@ describe('Mempool tests', () => {
 
         assert.isNotOk(mempool.hasTx(tx1.hash()));
         assert.isNotOk(mempool.hasTx(tx2.hash()));
+        assert.isNotOk(mempool._dag.hasVertex(tx1.hash()))
+        assert.isNotOk(mempool._dag.hasVertex(tx2.hash()))
+
     });
 
     it('should get tx by hash', async () => {
@@ -168,4 +172,19 @@ describe('Mempool tests', () => {
 
     });
 
+    it('should sort txns', () => {
+        const mempool = new factory.Mempool();
+        const tx1 = new factory.Transaction(createDummyTx());
+        const tx2 = new factory.Transaction(createDummyTx());
+        const tx3 = new factory.Transaction();
+        tx3.addInput(tx1.hash(), 1);
+        tx3.addInput(tx2.hash(), 2);
+        mempool.addTx(tx2);
+        mempool.addTx(tx3);
+        mempool.addTx(tx1);
+
+        const arrTxns = mempool.getFinalTxns(0);
+        assert.deepEqual(arrTxns,[tx2, tx1, tx3]);
+    })
+
 });