Abstract: The offshore platform power system is an indispensable part of the entire offshore oil and gas field development project. The submarine cable, as one of the important components of the power system, is responsible for transmitting electrical energy and connecting various devices in the system into a complete organism. Its safety and operational reliability are crucial to the entire offshore oil and gas field platform. In view of this, based on the development plan of an offshore platform in the Bohai Sea, the closing overvoltage of the submarine cable under different short-circuit capacities is simulated and analyzed based on the CloudPSS cloud platform, and shunt reactor is introduced to suppress the closing overvoltage, which provides a theoretical basis for the selection and parameter setting of submarine cables for marine engineering power systems.