Abstract: The paper uses FLUENT software to simulate the oxygen concentration field, velocity filed, the gas concentration field and pressure field in goaf. Through the comparison between simulation results and the field measured data, adjusting simulation parameters correspondingly, making final simulation results to consistent with field data, and the final oxygen concentration field and velocity filed are got. Finally, the goaf is divided into three zones with double index method (upper limit air leakage wind speed and lower limit oxygen concentration), the largest width of goaf spontaneous combustion zone is 41 m, and the calculated safety mining working face rate is 1.7 m/d.