The quality of frame type circuit breaker key accessory is directly related to the reliability of the circuit breaker. In order to accurately detect accessory’s electrical characteristics and improve product reliability, this paper selects electric operating mechanism and under-voltage tripping device as the main objects of study, and determines the required electrical parameters to be detected and failure criteria for the accessories; On this basis, the overall design scheme is given for accessories detection systems, and its hardware and software design are described. Breaker accessory test results show that the detection system can accurately detect the electrical parameters of the accessory and provide parameter reference in order to improve product quality and reliability.