Abstract: The deformation of rock mass includes the rock elastic deformation of rock block, plastic deformation and joint extension. Strength properties of jointed rock mass are closely associated with the development and extension of joints. This article, based on the damage mechanics and fracture mechanics theory, by simulating the expansion joints under different excavation conditions caused by changes of the damage tensor, explores the relationship between the rock mass strength and damage tensor to characterize the temporal and spatial variation of rock mass strength and anisotropy.