This paper presents a simulation method for investigating the failure of optocoupler equipment (OCEP) in multi-physical fields. The method is based on the aging of the solder layer of the photosensitive field-effect tube (PFET) and aims to analyze the performance degradation of the PFET. Firstly, a comprehensive multi-physical field model of the OCEP is developed using the actual structure of the CT test OCEP, taking into account the conductivity of the chip. Next, an OCEP failure simulation method is proposed, which takes into account the shedding of the PFET solder layer caused by the failure mechanism of the OCEP. Finally, the simulation results demonstrate that the degree of solder layer shedding reaches 70%, resulting in the failure of the OCEP.