Abstract: After excavation of underground engineering such as tunnels and so on, the surrounding rock mass generates a lot of persistent cracks. In order to maintain the stability of surrounding rock, the rock bolt reinforcement is usually carried out and the anchoring method has a direct impact on the anchoring effect. Based on a Coulomb strength criterion, the identification method of strength and failure mode of rock mass was established by comparing the location relation of a strength curve of rock and cracks in the   coordinate system. On the above basis, regarding the compressive strength of the anchoring rock as an objective function and bolting angle as the variable, the functional relationship of compressive strength of the anchoring rock mass with persistent cracks and bolting angle was set up. Thusly the bolting angle was obtained when the compressive strength achieved the maximum. And the fundamental method was presented to optimize the anchoring direction of rock mass with persistent cracks.