The influence of gas drainage to coal seam water infusion is discussed in this paper,based on the viewpoint that the permeability of coal seam can be improved and the resistance to water infusion can be cut down as gas drainage,the mechanism of enhancing effect of coal seam water injection due to gas drainage was researched. The result of field experiment indicated that after gas drainage if the same drainage holes are used for coal seam water infusion the effect of water infusion can be improved greatly,and drilling the amount of drilling can be reduced,so it is a kind of effective water infusion method.