Abstract: The characteristics of three-phase foam in mine fire control were introduced, its covering and inhibition were analyzed, and experiments on extinguishing the top fire in a porous medium were carried out. The results show that three-phase foam can cover the whole goaf and prevent everywhere fire by pervasion and accumulation. According to the characteristics of goaf and three-phase foam, technical parameters, such as diffused distance of three-phase foam, length between working face and pipe bottom and durative time for spontaneous combustion of coal, were deduced. Based on them, three-phase foam was applied in the workface N₂ 703 of Daxing coal mine in China, and laying pipes in advance in goaf was carried out. The effect of application shows that three-phase foam can successfully prevent spontaneous combustion of coal in the working face.