Abstract: This paper outlines the current application status of power supply protection for nuclear power plants. Focusing on the localization transformation project of the circulating water pump motor differential protection device, the following research is conducted: Firstly, the shortcomings of imported electromagnetic protection are analyzed, and it is pointed out that compared with traditional electromagnetic protection, microcomputer-based protection has advantages in five aspects: hardware stability, software flexibility, intelligence level, systematization capability, and maintenance cost. Secondly, combined with the on-site configuration of current transformers, the capacity of current transformers is calculated to verify the overload operation status, accurately locate the root cause of the problem, and propose solutions. Thirdly, the setting calculation of incomplete differential protection is carried out to determine the differential balance compensation coefficients of the current transformers at the machine terminal and neutral point of the differential protection device, ensuring current balance on both sides during normal motor operation. Finally, a creative proposal is made to utilize the circuit breaker position contact input to design an automatic engagement and withdrawal of differential protection. At the end of the paper, the research results are summarized, and future research directions for power supply protection in nuclear power plants are proposed from three aspects: application of intelligent protection devices, construction of power supply monitoring systems, and improvement of protection standard systems.