Abstract: In order to investigate the hydraulic sealing affected to the seam gas deposition law,take No. 11505 fully-mechanized coal mining face in No. 5 seam of Xian gshan Mine as the study object,from the water quality,fault features and roof and floor lithology,the paper analyzed the water sealing role affected to the seam gas abnorma I enrichment. The analysis results held that gas driving and sealing role caused by the underground water with static stored in the aquifer of the seam floor was the main ca uses to make the gas abnormal enrichment in the north part seam and floor of the mine field. The gas abnormal enrichment caused by the strata pressure driving and hydr aulic driving were the main causes to have the water and gas joint emission in No. 11505 gateway.