In order to increase the degree of the angular velocity tracking precision of the brushless DC motors control system, the controller is designed using the variable structure control with sliding mode. The mathematical model of the brushless DC motors is built. The sliding mode function includes tracking error and the differential coefficient of the tracking error. In order to alleviate the chattering, the saturation function replaces the sign function. The simulation result show the tracking precision is high and the controller output has not obvious chattering. The controller meets the tracking precision of he brushless DC motors control system.