The process of rock breaking with abrasive water jet (AWJ) is a nonlinear impact dynamics problem concerned with lots of factors. For the complexity of the process and the mesh distortion problem in dealing with large deformation problems with finite element method (FEM), the process of rock breaking with AWJ is simulated based on the coupling algorithm of smoothed particle hydrodynamics (SPH) and FEM. Combined with the simulated results, the scope of rock damage under 30% concentration of AWJ at different speeds is analyzed. In the analysis process, AWJ is simulated by SPH where the two different components of water and abrasive is achieved by editing Keyword File；And the rock is simulated by FEM which uses HJC cumulative damage model. The results show that the rock crushing pit has a funnel shape firstly. With the erosion pit deepened, a "bullet" body is formed by a "V"-shaped section and a circular cross section ultimately. During this process, erosion damage reduces sharply from the pit in the radial outward direction. Besides, rock erosion damage radius and the erosion pit radius decreases with the jet velocity decreases, and the ratio is between 1.8 and 2.2. On the whole, the results are basically consistent with the relevant results, and it provides a research method for rock breaking with AWJ.