Abstract: The high-voltage vacuum circuit breaker system of motor direct drive is used as a model, and the geometric constraints and motion characteristics of the high-voltage vacuum circuit breaker are derived from the kinematic and dynamic perspectives respectively, and the mapping relationship between the rotational motion of the motor rotor and the vertical motion stroke of the moving end of the arc extinguishing chamber is obtained. At the same time, the force analysis of the main moving parts of the high-voltage vacuum circuit breaker is carried out, and the load model of the motor direct drive operating mechanism is established. Simulation and experimental results show that the load analysis method of motor direct drive actuator proposed can provide theoretical guidance for the design of drive motor and converter capacity in terms of maximum torque demand calculation, and has guiding significance for the stroke curve planning of motor direct drive actuator.