Abstract: Taking a goaf as all directional same nature porous medium, a basic closed equation group of the gas flow field in the goaf was established.The FLUENT simulation software was applied to simulate the gas flow field within the goaf, analyze the gas concentration distribution features within the goaf under the different gas drainage conditions of the surface drilling boreholes .A study was conducted on the different negative pressure of the surface drilling boreholes affected to the gas flow fi eld in the goaf.The study found that the surface drilling boreholes located in the goaf with 2070 m near the air returning gateway would be favorable to the gas drainage and the negative pressure of gas drainage may bring a spontaneous combustion danger to the goaf.But with the certain monitoring and control measures, the 4050 kPa negative pressure of gas drainage could be acceptable.