Abstract: The SiCp/Al metal matrix composites have excellent properties such as high specific modulus, high specific strength, good wear resistance, high temperature resistance, good thermal conductivity and electrical conductivity, which make it become excellent substitutes for traditional metals in engineering applications. In this paper, our research is about machining SiCp/Al metal matrix composites with 45% volume fraction and establishing machining simulation model with finite element analysis. The machining mechanism was analyzed from the von mises stress distribution, the fracture and crushing mechanism of the particle and crack propagation on chip surface, and verified by milling experiments. The results show that the fracture and crushing of particles mainly occur in the shear zone and the separation surface between the workpiece and the chips. At the same time, micro cracks will occur on the chip surface due to the presence of particles, the propagation of microcracks is an important factor affecting the surface morphology of metal machining chips.