Abstract: Polycrystalline diamond tools (PCD) were selected to study surface and chip generation mechanisms during high-speed milling SiC-particle-reinforced aluminum matrix composites (SiCp/Al). The results show that feed marks, materials swelling and side flow, tool-workpiece relative vibration, pits produced during removing reinforment particles, micro-cracks and matrix tearing were the main generation mechanisms of SiCp/Al composites surface during high-speed milling. The machined surface quality could be improved by increasing cutting speed, using coolant, decreasing volume fraction of reinforcement particles, decreasing reinforcement particles size. The chip took uneven sawtooth-like, reinforcement volume fraction and heat treatment condition of matrix had remarkable effects on chip formation. The mechanism of chip were dynamic formation and expending of adiabatic shear, pits and micro-cracks.