High voltage disconnector is the largest switchgear used in power system. Mechanical faults of disconnector occur frequently, but there is a lack of effective diagnosis methods. In this article, the dynamic simulation principle and numerical calculation method are introduced, and the dynamic simulation model of the GW5-126 disconnector is established. Through the rigid flexible coupling dynamic simulation of GW5-126 disconnector, the simulation results of GW5 under normal state, jamming state and three-phase inconsistent state are obtained, the variation law of operating rod torque under different mechanical states is analyzed and summarized. The starting torque, meshing torque, meshing time, torque peak and torque peak time of disconnector under normal and fault conditions are compared, which has reference value for the mechanical fault diagnosis method of disconnector.