Abstract：In tunnel engineering，the strengthening water drainage as a design principle can not meet the demand of water environmental protection at present. However，it is difficult for the tunnel to endure huge water pressure when underground water is blocked up fully. By establishing interaction chain between tunnel engineering and water environment，the sluicing quantity of tunnel hole before lining is estimated with non–stable flow method. The scope，bulk，and deep draw-down of dewatering cone in aquifer above the hole are predicted. The permissible dewatering of tunnel lining for restoration of water environment is determined based on equilibrium equation of surface water，and the water pressure endured by tunnel lining is calculated based on discount coefficient method. In order to prevent and control water environmental hazard of ground above tunnel and sluicing hazard in tunnel a principle of ‘water environmental balance’with choking up underground water is summed up as a leading principle in tunnel design. Finally，the Yuanliangshan tunnel of Yu(Chongqing)–Huai(Huaihua) railway was analyzed as a calculating example.
