In order to ensure safe mining under waterproof coal pillars, theoretical calculation and numerical simulation were used to research mining feasibility in No.1 layer. Through theoretical calculation, it was clear that the maximum height of fracture zone after mining in No.1 layer was 60.12 m, thickness of protective layer was 13.36 m, and height of waterproof coal pillar was 73.48 m. The height of waterproof coal pillar was less than minimum distance of 128 m between No.1 layer and goaf water, which meant that mining in No.1 layer was feasible. Numerical simulation method was used to simulate development process and development height of overlying fracture zone after mining in No.1 layer, which showed that the maximum height of fracture zone was 56 m after mining, the minimum distance between the upper edge of No.1 fracture zone and upper goaf water was 72 m. It was stipulated in the regulations that thickness of protective layer under water body was about 14m, which was obviously that the distance between fracture zone after mining and the wave was greater than the safe distance. Therefore, we could draw the conclusion that mining was feasible.