Abstract: Abstract: Landfill will produce a variety of secondary biomass, of which methane and carbon dioxide are the mainstay, methane leakage and diffusion caused by the risk of fire explosion is extremely large. In order to avoid or reduce the occurrence of such safety accidents, taking a Beijing municipal domestic waste landfill as the research object, monitor the actual situation of leakage gas point under the cover film, and establish a corresponding three-dimensional model, the using of Fluent software to simulate the leakage and diffusion process of landfill gas in the atmosphere. The results show that the gas collection summary place and the slope of the pile in the landfill are the most prone to leakage, and the area where the explosion limit is reached in the standard state, the explosion hazard area is normally distributed within 0.5 m radial distance centered on the leakage source and 3.8 m longitudinal distance, and the wind speed is proportional to the radial distance of the gas diffusion and the longitudinal distance is inversely proportional. It provides a theoretical basis for the formulation of emergency countermeasures for gas leakage accidents in urban landfills and the layout of gas monitoring points.

Key words: Key words: landfill, methane gas, leakage diffusion, numerical simulation