Abstract: This paper deals with the numerical analysis of fracture mechanics for rock engineering. Some basic considerations have been taken for special application to rock mass with discrete joints. Under loading the joint propagation leads to the changes of physical-mechanical properties of rock mass, such as Young's modulus（E） and Poisson's ratio（v）, causing variation of the stress distribution and fractured scopes of joints in rock mass. The computer program of three-dimensional finite element has been compiled using the method of load increment based on the element transition principle. The rock abutment of an h dam of height 240 m has been analysed to evaluate the deformation, stresses and fracturing of rock mass.