Abstract: In order to solve a spontaneous combustion risk increased problems of coal left in goaf caused by air leakage quantity increased in the goaf due to gas d rainage in a high level gas drainage gateway, according to high gassy and easy spontaneous combustion features of the mining operation in No. 1502 fully- mechanized top coal caving mining face in Zhengxing Mine, a combined method with a site measurement and a numerical simulation was applied to simulate a gas concentration fie Id, air leakage field and oxygen concentration field in the goaf occurred in three high level gas drainages under the conditions of no nitrogen injection and gas drainage measures, gas drainage in the high level gas drainage gateway and nitrogen injection in the goaf with Fluent software. With the Fluent simulation technology, three zon es distribution in the goaf could directly obtained with a heat radiation zone of 0 ~ 23 m, oxidation zone with 23 ~ 69 m and suffocation zone over 69 m. A spontaneous combustion danger area in the goaf was determined as 23 ~ 69 m. Finally, an evaluation was conducted on the nitrogen injection effect and gas drainage negative pres sure and a fire prevention and control system of the gas drainage in the high level gas drainage gateway under the nitrogen injection condition of the goaf was improve d.