Based on the initial elastic and divisions of work by static and dynamic loads, the hard and intact brittle rock breaking process under static and dynamic loading is divided into 3 stages: elasticity, damage and fracture, which are analyzed by comprehensive use of elastic mechanics, rock mechanics, damage mechanics and fracture mechanics. By the elastic half space stress field and shear failure of the rock unit under the concentrated force, the damage of rock crack source and its curve extension path are found; typeⅠ and type Ⅱ cracks are selected as press shear crack extension modes under dynamic load impact. Method to define the damage degree by impact energy (times) is put forward. The lateral crack propagation and coalescence of adjacent pit is defined as the end of rock breaking. This mechanical model can be applied in the system simulation, numerical simulation and machines design for rock breaking by combined static and dynamic loading.