Abstract: In order to accurately determine the reduction factor of water pressure acting on tunnel linings, a method to determine the water load acting on the composite linings and the water discharge in the tunnel is derived based on the correlation theory of groundwater hydraulics from the groundwater seepage action by means of the groundwater treatment regulations in the tunnel codes and the empirical methods. The influences of variable parameters of primary support, secondary support and grouting circle on water inflow and reduction factor of external water pressure are released by using the theoretical analysis. The problems which should be paid attention to and the methods to determine the value of reduction factor of water pressure acting on different kinds of tunnel linings are studied. The results may provide references for the design of tunnel waterproofing and drainage system in high water pressure regions.