This paper introduces a trip fault caused by intermittent spark discharge of a 40.5kV solid-sealed vacuum circuit breaker in salt spray environment. Through the fault inspection and fault cause analysis before and after the breaker disassembly, it is found that the main cause of the fault is serious salt pollution on the surface of the product caused by the salt spray environment, which causes intermittent spark discharge and insulation aging on the surface of the product, leading to trip failure. According to the specific cause of the fault, the corresponding solution is put forward, and the practice is verified, and the insulation problem in the salt spray environment is fundamentally solved.