Abstract: A simulation model for a combined diesel or gas turbine (CODOG) propulsion system was built in Matlab/Simulink, and the veracity of this model was validated using the trail data of actual ship. Through the model, two existing accelerating control approaches were simulated and their flexibility was evaluated. The result shows that during the emergent accelerating process, the main engine is overloaded seriously; during the natural accelerating process, however, the redundancy of the engine power is big and the flexibility is low. To improve the flexibility, a method using PI controller was proposed to design the "engine-propeller" combined control curve of the accelerating process. In this method, the controller uses the engine power redundancy to adjust the increasing ratio of engine speed and propeller pitch during the accelerating process. Simulation result shows that using this method to control the accelerating process, the engine overloading can be avoided, and the increasing ratio of the ship velocity is about 70% faster than the natural accelerating process.