Abstract: Based on finite difference method,the numerical simulation analysis on under-protecting coal stratum in Liyazhuang mine is carried out,the stress distribution,deformation laws and pressure-relief protective range of protected coal seam are achieved.Meanwhile,according to the simulation results,using water inrush coefficient method of effective waterproof layer to divide water inrush risky area of under-protecting coal stratum,the feasibility of protective coal seam mining is analyzed and judged.The results show that the under-protecting coal stratum is not feasible when the pressure-relief protective angle reaches up to about 50°after mining under-protecting coal seam.