Abstract: In this paper, an equivalent continuum model for rock mass which consists of joints and rock is proposed by averaging the stress and strain of rock mass in a volume element. Using the theory of damage mechanics and fracture mechanics, the damage tensor, effective stress tensor and damage strain ,etc. of rock mass are defined, propagation equation of damage is developed. Furthermore, the damage fracture model for jointed rock mass is established. The fracture mode of joints is studied by model tests.