The distribution of abrasive particles in fluids is an important research topic in the study of abrasive waterjet cutting processes. However, it is impossible to obtain the accurate distribution law and influencing factors by performing only experiments; therefore, it is necessary to study abrasive waterjet cutting processes with the help of numerical models. The existing numerical models usually adopt the form of artificial settings for the distribution of abrasive particles in fluid. This method cannot accurately simulate the random distribution of particles. In this paper, the random algorithm method is used to simulate the impact azimuth and the random distribution of abrasive particles in water. The smoothed particle hydrodynamics (SPH) method is used to simulate the distribution of abrasive particles and the process of jet impingement. The influence of the particle distribution on the simulation results is studied. Comparisons show that the dent formed by the jet impinging on the target with random abrasive particles is similar to the dent from the actual cut, and the contour distribution of the dent is more uniform than that of the cut. The simulation results obtained by the SPH method are accurate.