Abstract: In order to improve the safety of separation test of mine-used disconnecting switch, the product inspection cycle was shortened and the technology of brushless DC motor was proposed. Based on the analysis of the electromechanical accident conditions and mine-used disconnecting switch structure, working principle, we analyze the working process of the pneumatic institutions and shortcomings in detail. Through the analysis of the reaction curve, we obtain the output torque trend of motor mechanism, design the electromagnetic structure of the motor mechanism, establish the finite element simulation model, and simulate and analyze no-load current, no-load magnetic chain, no-load torque and load torque of the motor.