Based on the engineering geology survey of the area with critical sliding rock blocks in the south opencast slope at Huidong lead zinc mine,a stability analysis on the sliding blocks was carried out by the 3 dimension wedge vector analysis method.Accordingly,the reinforcement measures such as long pre stressed cable bolting,concrete stopping and water control were taken.Through monitoring for several years and testing by mining operation,especially in rain season,it was proved that the control and treatment of slope was successful.