Initial stress anchor wire anchoring technology has the merits of fast speed, small perturbation and economic when healing unstable rock side slope. Choosing the spacing, position, angle of reinforcement anchor wire plays a vital role in reinforcement stability and economy. The landslide of an open pit was elected as project background in this paper. Operation model was set up by Lagrange arithmetic which analyzed the reinforcement mechanic and broken pattern of anchor wire. And it defined that the optima spacing is 8m. The anchor wire reinforcement angle and institution position research were researched by using limit balance theory. The optimum design angle obtained is -20°~20°, and the optimum institution position is in the range of 1/5~1/2 of the lower reinforcement side slope height.