由于预应力锚索可以改善岩体的强度性质、提高岩体的整体性、减小岩体的变形，使岩体达到要求的稳定安全度，因此被广泛应用于复杂岩质边坡治理工程中。预应力锚索设计参数的选取，如锚索吨位、锚索长度、锚固角、锚索间距等直接影响着边坡加固技术的可靠性和经济上的合理性。采用刚体极限平衡法，给出了考虑预应力锚索时的安全系数公式；推导了在获得相同抗滑效果的前提下，使得锚索长度最短的最优锚固角公式；研究了锚索设计优化流程：先求出最优锚固角，然后在最优锚固角下调整锚索长度；以某工程为例，实现了锚索优化设计，验证了优化流程的可行性和合理性。

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.