Task allocation is one of the core steps to effectively exploit the capabilities of cooperative control of multi-UCAV. Factors that effect the three key tactical objects, target value damage, UCAV attritions and task expending time are analyzed. By integrating the two typical instances in combat, that is multi-UCAV attacking the same target simultaneously and using soft kill weapon systems, a multi-UCAV cooperation task allocation model for attacking task is formulated. A new algorithm based on the principles of particle swarm optimization is proposed. Simulation results indicate that the task allocation model formulated in this paper is rational and the PSO based algorithm is effective.