Abstract: According to the migration process of the leakage gas in the soil of the buried gas pipeline, the convection and diffusion law of the leakage gas in the soil is studied based on the FLUENT software. It is found that the leakage gas will form an ellipsoid high concentration area in the leakage port of the pipeline, and the transverse diffusion with the concentration difference as the main driving force is less than the longitudinal convection with the pressure difference as the main driving force. This conclusion is consistent with that of full-scale experiment. The effects of soil properties, including soil porosity, soil moisture content and soil density on the behavior of gas convection and diffusion were studied based on the scale of the diffusion radius of the lower explosion limit of methane and the mass fraction of methane on the ground. The simulation results provide a reference for risk assessment, emergency evacuation, pipeline design and construction.