A computer simulation method for predicting the dynamic responses of a marine power system containing both AC and DC subsystems is proposed. The method has two important features. First, it allows modelling of system components in modular form and representation of network relations by utilising Kirchhoff's current law, hence providing flexibility in model building and testing. The second feature is its ability to simulate the performance of DC machines and converters in a combined AC/DC system. The paper contains a description of the method and its application to a practical marine power system. Simulation results are practically verified by comparing with a manufacturer's supplied experimental data.