Aiming at the cooperative task allocation problem of unmanned aerial vehicle (UAV) cluster, a multi-objective multi-task allocation mathematical model is constructed with the optimization objectives of minimizing the total range of all tasks completed by UAV cluster and the number of unfinished tasks, and an optimization method based on chaotic ant colony algorithm is proposed to solve the model. Based on the idea that hybrid algorithm can improve the performance of single algorithm, the ergodicity and randomness of chaos algorithm and the positive pheromone feedback mechanism of ant colony algorithm are combined in the cluster task allocation problem, and the simulation experiments are carried out to verify the effectiveness and applicability of the proposed method. The results show that the cooperative task allocation method based on chaos ant colony algorithm can enhance the global optimization ability, improve the efficiency of the algorithm, and allocate the optimal task sequence for multiple UAVs.