Abstract: The initial closing speed characteristic of the actuator is a key factor affecting the closing reliability of the vacuum circuit breaker. In order to reduce the dynamic impact and achieve reliable closing performance, the spring operating actuator of a 10 kV AC vacuum circuit breaker is taken as the research object, the initial closing motion characteristics of the vacuum circuit breaker are determined as the design goal, and the response surface method is applied to optimize the cam structure parameters. The motion characteristics have been optimized by adjusting the cam structure parameters and the preload of the closing spring. The comparative analysis results indicate that under the premise of ensuring the motion characteristics of the actuator, the reliability of the closing operation can be improved by optimizing the cam with the initial closing speed.