As the largest coal producing and consuming country in the world, the safe production of coal mine in China is related to the long-term development of coal industry of China, and mine fire is one of the most serious safety problems. Taking Dashe Coal Mine as an example, this paper studies the regularity of various gases released from coal sample in the programmed-temperature heating experiment, including CO, O2, C2H2 and C2H4, etc. Based on the data of programmed-temperature heating experiment, the function curve of the gas concentration and temperature of coal sample is fitted. The change of CO concentration is most obvious with the increase of temperature, which can be selected as the index gas to monitor the coal spontaneous combustion in goaf of Dashe coal mine. The distribution of oxygen in goaf under different number of faults and different volume of air leakage is simulated by FLUENT software. The oxygen concentration of 8% and 18% is taken as the criteria for dividing the three zones(heat dissipation zone, oxidation zone and suffocative zone) of goaf. With the increase of the number of faults, the width of oxidation zone in goaf increases, which makes it more difficult to prevent coal spontaneous combustion in goaf. According to the mining data of Dashe coal mine, the quantity of nitrogen injection needed in goaf was calculated, and the effects of different nitrogen injection locations before and after passing through faults on oxygen concentration distribution in goaf were simulated respectively. In addition, the oxygen concentration in goaf in y=0m, y=60m and y=120m was monitored by the monitoring pipeline system. It was found that the fault in goaf reduced the effect of nitrogen injection.