Residual current operated circuit breaker directly affects the safety and reliability of low?voltage distribution system. In order to study the reliability of residual current operated circuit breaker, the performance degradation process is studied by using the modeling method based on degradation distribution, and its service life is predicted. Firstly, the failure mechanism of residual current operated circuit breaker is analyzed, and then the accelerated degradation test of residual current operated circuit breaker is designed and implemented. The reliability analysis model that the degradation quantity obeys the normal distribution is established, and the parameters in the model are estimated by the least square method, so as to evaluate the reliability of residual current operated circuit breaker and draw the reliability curve.