Abstract: The transient process of fuel switching is simulated to study the problem of combustion instability and excessive speed fluctuation in the process of fuel switching. The model of dual fuel engine with fuel switching control is built with mean value method according to the thermodynamics principle. The model is verified through engine bench tests. The transient of fuel switching process is simulated with the model and the transient performance and response of the engine is exhibited. Tests show that the model satisfies the requirements of engine manufacturers in accuracy and rapidity.