Abstract: Quaternary gravel aquifer and the goaf water are the main threat of safety mining of steeply inclined thick coal seam with fully mechanized top coal caving mining in Meihe mining area.It is an important problem to be solved.Taking Mitsui 5109 zone as the research area，based on the transient electromagnetic sounding and the goaf water of and the failure height prediction on horizontal overburden of the steeply inclined thick coal seam，abundant coal pillars for the water barrier at F4 fault are set.In the light of the strata movement law，it is calculated that the mining influence in working face spread to the goaf water area.The evaluation shows that:before mining，the elevation of goaf water just declined to +172 m can ensure the safety mining.

Key words: Goaf water, Steeply inclined, Horizontal layering, Fully mechanized top coal caving