Abstract: The wedge stability analysis method specified in the Gravity Dam Design Code of China was discussed.Based on the mechanical mechanism of the traditional rigid limit equilibrium method,the correct expressions of action and resistance were educed and the directions of vectors were presented.A new approach of equal safety degree was proposed for the calculation of reliability index of gravity dams.Then,a safety formula and its allowable index were presented,and a set of corresponding partial coefficients,whose rationality were proven were also proposed.