Abstract: By adopting FE numerical simulation, the influence of water table line on the distribution of pore water pressure around the shield tunnel face is studied, and the influences of water table line, tunnel diameter, tunnel depth on the seepage force are obtained. The results show that the seepage force varies almost linearly with the water table line. By considering the average seepage force on the slide block, the face stability of shield tunnels is studied via trapezoidal wedge model, and a formula to calculate the limit support pressure under seepage condition is deduced. The seepage force shows great influence on the limit support pressure, and the total support pressure increases almost linearly with the water table line. The proposed model is used for the Qianjiang river shield tunnel project to calculate the limit support pressure of 5 selected typical sections, and the variation of support pressure is obtained.