Abstract: Along with the expanding of the hydropower project scale, the stability issues of high rock slope under the complicated geological conditions are increasingly prominent. Since the pre-stressed anchorage cables can enhance the mechanical strength and the integrity of the rock mass, reduce the deformation of the rock mass ； and make the rock mass stable and safe ； the pre-stressed anchorage cables are widely applied to slope engineering . The selection of the design parameters, such as cable tonnage, cable length, dip angle of the cable, interval of the cable and so on, directly affects the reliability and economic rationality of the reinforcement. In this paper, firstly, the rigid body limit equilibrium method is adopted to obtain the formula of safety factor considering the pre-stressed cable. Secondly, the optimum dip angle formula, which makes total length of the cables to be the shortest under the condition of obtaining the same anti-sliding effectiveness, is deduced. Thirdly, optimization design process of the cable is formulated including two major steps: The step 1 is to find the optimum dip angle of the cable, and the step 2 is to adjust the length of the cable according to the optimum angle. Finally, taking a rock slope project as an example, the optimization design of the cable is carried out, by which the feasibility and the rationality of the optimization design process are verified.

Key words:  complicated rock slope  ,   stability analysis  ,   pre-stressed anchorage cables ,   , optimization design  ,  optimum dip angle of the cable