To evaluate the reliability of Multiagent system accurately,a synthetic evaluation approach considering communication reliability,unit reliability and system topology is proposed. Multiagent system structures are summarized; the influence of communication reliability and unit reliability to the reliability of centralized, distributed and federated Multiagent system is analyzed based on Markov process; and system reliability models are given. The simulation results show that this method can simplify the problem of complex system reliability, for the entire system reliability can be obtained after the reliability of every part is achieved.