Abstract: In view of the situation that the spontaneous combustion in goaf is possible due to the excessive coal mining of 8204 fully mechanized working face in Kouquan Coal Industry. In combination with the actual conditions of the working face, the marked gas detection and the comprehensive fire preventing and extinguishing technology of nitrogen injection as the main and grouting injection and spraying resistance agent as the auxiliary are determined. Through the analysis of coal samples, it is determined that 8204 working face is identified with CO as the signature gas and C₂H₄ as the auxiliary indicator to judge the spontaneous combustion of coal seam in goaf. After the integrated utilization of fire prevention measures in the process of mining, the CO concentration at upper corner of working face is（5～10）×10^-6, do not detect C2H4, the CO concentration at return air is（0～2）×10^-6, which effectively guarantees the safety mining of mining face.