Abstract: Based on the limit equilibrium theory and the hypothesis of planar sliding surface,a formula for calculating the angle of shear failure was deduced considering cohesion and cut slope angle.It was indicated that there was no relationship among the angle of sheer failure,the cohesion of soil and the depth.However the angle of shear failure was linearly related with the cut slope angle and the angle of internal friction of soil.And then a formula was proposed to compute the lateral soil pressure of soil nailing wall.Finally,it was proved that the formula for the lateral soil pressure could be used to soil nailing walls with different cut slope angles for both cohesive and noncohesive soils.