The power supply laser in electronic current transformers is a semiconductor device that supplies energy to the remote module. In order to solve the problem of frequent failures，it is necessary to study its degradation mechanism in order to provide feasible ideas for improving device reliability. A comprehensive testing system for the external characteristics of semiconductor lasers is designed. By using a constant temperature heating box and a vibration table，the PIV curve，wavelength and other external characteristic parameters of the laser can be measured at different temperatures and vibrations. Through correlation analysis，the impact mechanism between the key parameters of slow degradation and environmental sensitive parameters is demonstrated. Secondly，the failure characterization of the faulty optical chip is carried out to determine the degradation mechanism of the power supply laser. Finally，exponential fitting is performed on the optical power of lasers with different degrees of degradation to obtain an expected lifespan of 127 438 hours under operating conditions，and maintenance improvement measures are proposed. The research results show that the slope efficiency of the degraded laser changes significantly up to 7.99%，and the threshold current changes by 4.98%. The two parameters are strongly correlated with laser degradation. The main reason for chip degradation and even failure is that the damage of the cavity facial mask layer continues to intensify，leading to optical catastrophes on the cavity surface.