In the wireless sensor networks trust model, aiming at the problem of the dynamic change of trust value with time and context, this paper proposes a trust model based on dynamic change of node behaviors. The model provides a calculation method of direct trust and indirect trust, and integration of trust value, the transfer of trust, and also gives a trust update mechanism based on the sliding time window. The simulation results show that, the trust value is punished and adjusted by the dynamic change of the communication behaviors between nodes, and the resulting trust value can be more sensitive to the behavior change among the reaction nodes, and more accurate and reliable for the evaluation of the trust relationship between nodes.