In order to facilitate the 3D simulation research，the underwater excitation process of the air-gun seismic source is simplified to the pulsation of the high pressure water bubbles. A 3D digital model of high-pressure air bubble in water was constructed with ANSYS AUTODYN software to study the pulse effect of the air bubble，and the calculation was conducted under different height and boundary conditions. From the results we know that high-pressure air bubble can induce shock wave and bubble pulse pressure wave，and the bubble pulse frequency and the pressure peak both become bigger with the depth increase of the air bubble，but the pressure increase rate becomes smaller. The rigid boundary condition of finite water area with large enough size can increase the bubble pulse frequency and the pulse pressure. In particular，the bubble pulse frequency and pressure will be decreased if the bubble is close to the bottom. The simulation results of this paper show that the 3D simulation method is feasible and can be used for the simulation of the plane and solid complex combinations of air-gun arrays with the effect optimization of the air-gun earthquake source.