Abstract: Through a real circuit breaker fault, the reason of the delay of the spring mechanism circuit breaker in the process of opening is expounded.Combined with the background data analysis of substation intelligent terminal, the whole process of mechanism action of this type of circuit breaker after operation is analyzed.At the same time, combined with the mechanical action characteristics of the circuit breaker, analyze and judge the fault components and fault causes.Finally, it is concluded that the form of the coil and iron core of the circuit breaker is unreasonable, and the tripping mode of the mechanism has defects, resulting in the failure of the circuit breaker to act in time.At the same time, an improved opening and closing coil is proposed to improve the opening and closing stability of the circuit breaker.