Abstract: Plastic shell circuit breaker is a very important protective device in low voltage distribution network. Its reliable and sensitive action is essential for the safe and stable operation of low voltage power supply system. Based on the analysis of the working principle and operation process of low voltage plastic shell circuit breaker, the operation mechanism is calculated and modeled, and the process simulation and optimization design are carried out by Pro/E three-dimensional software, which can not only ensure the sensitive and reliable operation of the circuit breaker, but also reduce the volume and cost of the product.