The calculation method of direct-current (DC) short-circuit current and analysis of selective protection of fuses are important aspects of the design of the DC integrated power system. The design directly affects the selective protection scheme of fuses in the DC distribution system and the operational stability of the DC distribution system. The calculation principle and method of the single module short-circuit current in marine DC distribution system are presented for equivalent calculation of the ship’s DC distribution system. By selecting different short-circuit points, the impact of different short-circuit points on the DC comprehensive power system during short circuit. The short-circuit currents of different branches are calculated to determine the fuse specification through the actual I2T curve of the branch. The error between the simulation results obtained from the equivalent model simulation and the practical calculation is within 1% by analyzing the practical examples. By using the MATLAB/SIMULINK equivalent model simulation method, the calculation of the short-circuit current of the DC distribution system and the reasonable selection of the fuse can be conducted without establishing a detailed SIMULINK model and performing tedious formula calculations.