Drainage segment lining is a new structure type formed by setting up drainage holes on the conventional segment lining. Based on continuum fluid-solid coupling analysis model of fractured rock mass, the distribution patterns of water pressure behind the lining walls and in surrounding rock are studied under three kinds of water pressure, while the segment lining with double drainage holes at each side of one ring has been applied. The results show that the water pressure behind segment lining wall could be effectively reduced by setting up drainage holes, and the pressure distribution patterns are in horseshoe shape approximately. The reduction effect of water pressure is more and more obvious from the tunnel crown to the elevation where the drainage holes are provided. But the drainage hole leads to uneven distribution of water pressure, causing the increase of local moment. So, more attention should be paid to the drainage segment lining during design.