Abstract: In the mining process of lower seam of 11^#, 12^# merged coal seam in 307 district of Meiyukou Coal Mine of Datong mining area, affected by "two hards" condition and rock burst, the fire disaster occurred and the whole district was closed. Through monitoring various gas components of 1^#、4^#、8^#、9^#、10^# in 307 district, it used single gas concentration change rate indicators to analyze the combustion state of closed fire area, and used the quantitative analysis and calculation of gas component rate RT to judge the possibility of fire resurgence when the closed fire area was unsealed. The analysis showed that, the fire sources in closed fire area were basically off, however, there were high-temperature ignition points and the possibility of fire resurgence after unsealing. Aiming at the analysis results, it proposed the unsealing program and took construction for 8702 lower working face of 307 district. During unsealing the closed fire area, the change of gas components was little, and the state of fire area was basically stable.