Abstract: The stability analysis of the rock pit slope belong to Nuclear island in Haiyang Nuclear Power Plant is carried out by qualitatively and quantitatively.There is a large-scale hoisting equipment with large loading load on the top edge of the rock pit slope.The strike of the slope is cambered.Firstly,according to the stratum lithology and geological structure features of the site,the plane sliding,wedge failure and toppling failure of the slope are qualitatively analyzed by stereographic projection.The range and mode of failure may be determined preliminarily.On this basis,the means of the limit equilibrium,the stability of the plane sliding and wedge failure mode is analyzed quantitatively.The limit equilibrium is also used to analyze the stability of the slopes reinforced by anchors.Stated thus,the different failure modes may occur in different slope areas.The probability of occurrence of wedge failure is the greatest.The effect of the anchor rod on the stability of the wedge is obvious,especially for the less stable ones.