Abstract: In this paper, it introduced that mining the fourth coal seam of 2024 repeated mining face(B₂) in Baijiao Coal Mine, coal seam thickness was 1.1~ 5.9 m, the average thickness was 3.5 m. The part of top coal seam had been exploited in the period from 1978 to 1984, the average thickness of residual coal was 1.4 m. Because residual coal was so much in goaf, resources waste was serious, it was ready to carry out repeated mining in goaf. But the air leakage of goaf was serious, the residual coal generated pre-oxidation, it appeared local high temperature, CO and other iconic gas, so there was the great risk of spontaneous combustion for the residual coal, which posed a serious threat to the repeated mining. Combined with the actual situation of 2024 repeated mining face in Baijiao Coal Mine, it used two kinds of fire prevention and extinguishing technology, they included the mobile grouting colloid injection and the direct liquid carbon dioxide perfusion underground, which effectively solved the problem of spontaneous combustion during the mining of working face, it achieved the successful mining in the working face, and withdrawing the support safely.