Abstract: This article describes the handling process of an abnormal event involving the failure of a circuit breaker''s anti-tripping mechanism. Through the elimination method, it was determined that the cause of the anomaly was the competitive relationship between the anti-tripping relay of the circuit breaker''s main mechanism and the auxiliary contacts of the circuit breaker, which prevented the anti-tripping relay from operating reliably, resulting in the failure of the anti-tripping function. By adjusting the wiring of the circuit breaker''s auxiliary contacts, the risk of anti-tripping failure was eliminated, and a correct inspection method was established. This provides certain reference value for on-site maintenance.