Submarine cable terminal voltage is an important parameter for the implementation of voltage withstand test. In order to assure the safety and effectiveness of the wiring test of the voltage withstand test, the accurate calculation of the cable terminal voltage is particularly critical. A 220 kV submarine cable of a wind power plant in Jiangsu is considered. Firstly, the distribution parameter model is established and the formula for calculating the voltage along the singlephase cable is deduced. Then, the influence of armor layer and other twophase cables is considered. Combined with the equivalent model of capacitance between different layers of threephase cable, an improved calculation model of submarine cable based on the end parallel equivalent capacitor method is proposed to improve the calculation model so that the terminal voltage can be accurately calculated. Besides, the practical calculation equation of the terminal voltage is also verified by the accurate simulation results of PSCAD/EMTDC software, validating that the calculation equation of the terminal voltage for the submarine cable withstand voltage test deduced is accurate and convenient. It is of great significance to ensure the safety of the withstand voltage test connection scheme.