Abstract: In order to predict pressure fluctuation of the diesel fuel injection system accurately, the gas bubble model based on gas bubble resolving and releasing physical processes was applied to the diesel fuel injection system model, and simulation program of diesel fuel injection system model was presented. The diesel fuel injection system model with the constant void fraction and the gas bubble model were simulated respectively, and the simulation results were compared with experimental data. The results showed that the simulation result curve of the diesel fuel injection system model with constant void fraction was smooth. But for the model of fuel injection system simulation with gas bubble, the simulation result was more coherent with the experimental data because the gas bubble volume varied with system pressure and time, particularly when the pressure exceeded 45 MPa, and the increasing of reduction rate of gas bubble volume caused the pressure shock. The study not only verifies the application feasibility of gas bubble model in diesel fuel injection system, but also provides reference for diesel fuel injection system model under two-phase condition.