In view of the weapon target assignment（WTA） problem and its characteristics,this paper puts forward a quantum particle swarm optimization algorithm with discrete mapping. First of all,a target allocation model is established for the damage benefit obtained by the weapon system in the target attack process. A method of coding adjustment based on discrete mapping is proposed to project the continuous particle position vector onto the discrete space to avoid the noncompliance of the model constraint solution for improving particle utilization. Through comparison of simulation validation,the improved algorithm has superior speed of convergence and stability. The experimental results show that the proposed method can effectively solve the WTA problem.