Abstract: Based on commercial CFD software FLUENT, the component transport model and k-ε turbulence model were selected, and the PISO solution method was used to simulate the leakage and diffusion process of natural gas with methane as the main gas in air. The numerical simulation results of different pipe pressures and different leakage ports are obtained. The numerical simulated results of natural gas leakage are basically consistent with the calculated results based on the small hole leakage theoretical model. The results show that the pressure and leakage in the pipe are linear, and the diameter and leakage of the leakage are quadratic. The height of the jet generated by the leakage increases with the change of the pressure inside the pipe and does not change with the diameter of the leakage.