Abstract: The hydrogeological conditions of the lower group coal in the 16th mining area of Hegang Coal Mine are complex. It is threatened by the high confined water of the thirteenth to fourteenth limestone water and the Ordovician limestone water in the floor and belongs to mining under pressure. In order to solve the problem of the great influence of water disasters during the mining of the lower group coal seam and avoid major hidden dangers, the horizontal sump was transformed and expanded according to the current situation of the mine drainage system. Through the combination of theoretical calculation and practice, a method of combining the direct drainage system design and the relay drainage system using the original drainage system and pipelines was proposed to improve the drainage capacity of the mine and meet the needs of safe production in the mine.