To solve the problem of low efficiency of probabilistic packet marking, an improved algorithm was proposed.This new algorithm optimizes the encoding of path information and modifies the marking and reconstruction process, so that victims can quickly reconstruct the attack path.Simulation results have shown that the new algorithm can effectively reduce combination frequency, improve tracking efficiency and greatly reduce the false positives rate.In the actual denial of service attack, victims can track the attacker faster and more accurately, thus minimizing the damage.