Task assignment algorithm research is an important direction in multi-agent research. The traditional contract-based task allocation algorithm has a low efficiency problem, and the problem will be more prominent in a dynamic environment. In the dynamic environment, an improved contract network method is proposed for the task allocation algorithm of multi-agent system. This method considers task familiarity and load balance, and improves the efficiency of multi-agent system allocation. Simulation results show that this paper shows that the method improves the system revenue.