Though research on multi-agent systems have progressed at a steady pace, its promise has yet to be realized. One major difficulty is that, by its very nature, the multi-agent system is a large, uncensored system. This raises the question of how much dependability to give each information source. We cannot expect each user to know the trustworthiness of each source. Trust mechanism is regarded as a key for solving the problem of security in multi-agent systems. To achieve the trust management autonomy, this paper presents an autonomous trust construction model based on Bayesian method. The presented model adopts the Bayesian method to evaluate the trust value of each agent, and uses the graph theory to combination and path searching to construct the trust relation. The simulation experiment results prove that the autonomous trust construction is effective.