Abstract: The mechanism was understood in-depth that coalfield fire area gas invaded into underground working face, which had important significance to ensure the mining safety of underground working face.Taking the typical working face affected by the overlying coalfield fire area of Wuhai mining area as the research object, some influence factors for underground ventilation system were considered, such as topography, surface wind speed, temperature difference between day and night, changes in atmospheric pressure, formation fracture and fire-blow pressure. The CFD method was used to study the gas flow regularity between coalfield fire area and working face, the results showed that excessive air static pressure was not conducive to the prevention and control work of coal spontaneous combustion; CO₂ could be considered as the early warning indicator of overlying fire area gas invading into underground working face; the air pressure difference between coalfield fire area and working face was the root cause of gas flow.