SiCp / Al composites have excellent physical properties but it is difficult to process SICP / Al composites due to the presence of particles. The superhardness and wear resistance of particle materials damage to the machined surface and tool wear are considered to be main obstacles to the processing of such particle composites. Objective To address the challenging machinability of SiCp / AI composites the machining mechanism was studied by comparing conventional cutting CC with ultrasonic elliptical vibration cutting UEVC and the effects of particle damage on chip formation and surface quality under the two machining methods were analyzed. Methods The cutting model was established based on the actual microstructure of SiCp / Al composites and the finite element simulation method was used to show the cutting process from the microscopic level which was able to intuitively show the effects of particle damage on chip formation tool wear and surface quality under the two machining methods so as to predict the problems that may be encountered in the actual machining process of composite materials and to propose corresponding solutions. Results CC machining is serrated chips the cutting process is mainly two-body sliding friction of particles to the tool and adhesion friction of the aluminum matrix and the underground damage caused by the machining is serious. However during UEVC machining the chips are easily separated into segments the cutting process is mainly three -body rolling friction of particles to the tool and particles gathered at the root of the chip are less compared with the CC processing weakening the damage to the machined surface. Under the two machining methods the machined surface has the following defects particle breakage particle protrusion large cavities pits and grooves. Conclusion Overall UEVC machining is beneficial to chip breaking resulting in fewer damage defects and smaller particle damage and can significantly reduce cutting force which has a certain effect on improving the machining surface quality of SiCp / Al composites.