Abstract: In corresponding to the poor efficiency of traditional drainage method in low penetration coal mine and disadvantage of bad sealing property, gas drainage in high level drainage tunnel by water sealing system(GDHTWSS) was proposed under the basis of the pressure distribution in working face, the mechanism was then discussed. Taking No. 1111(1) fully mechanized coal face in Zhangji mine as a example, the pilot test of GDHTWSS was conducted in the mine, and numerical simulation of FLAC was used to decide the range of caving zone and fracture zone. The result indicated that the GDHTWSS was feasible to apply in low penetration coal mine, which has the advantages of high concentration drainage and stability. Furthermore, it can enrich the experience of gas treatment in fully mechanized coal face.