Based on the difficult machinability of Al/SiC_p composite materials, a two dimensional finite element cutting model was developed in this paper. By using ABAQUS, the dynamic simulation of the cutting model was performed. Comparison of the result of simulation and experiment, the accuracy of the cutting model was verified. And then, the distribution form of SiC particle, the diameter of particle and the edge radius of tool effect on the cutting force were analyzed based on the model. The results show that the distribution form of SiC affects the chip morphology and the cutting forces are obvious, and particle clusters is not helpful for composite materials machining. The cutting force decreases with the increase of particle diameter, while increases with edge radius of tool.