Aiming at the problems of weak survivability and poor scalability of traditional centralized target assignment algorithm, a fully distributed multi-platform collaborative target assignment algorithm based on improved contract net protocol is proposed. According to a series of constraints such as operational environment constraints, task constraints and fire platform performance constraints, the target allocation model is constructed. In the process of target allocation, contract exchange operation is added to improve the allocation revenue. The results show that the algorithm can improve the overall revenue, reduce the target allocation response time, and has good scalability.