In order to explore the microscopic cutting mechanism of carbon fiber reinforcement plastics (CFRP),the zero thickness cohesive element was used to simulate the interface phase by finite element method.The carbon fibers were cylindrical and randomly distributed in the matrix to reflect the microstructure of CFRP.Different constitutive rules,material failure and evolution criteria were set up for each constituent phase.Four typical orientation (0°,45°,90° and 135°) were simulated to investigate the microscopic cutting mechanism of unidirectional carbon fiber reinforced plastics (UD-CFRP) under different fiber orientation.The results show that the microcosmic damage of CFRP is different at different fiber orientation.Interfacial cracking and fiber breakage are the main failure modes in cutting 0°CFRP,tool invasion is the main failure mode in cutting 45°and 90°CFRP,fiber breakage and cracks along fiber direction occur in cutting 135° CFRP,fiber breakage point is below the edge of the tool. Finally,the accuracy of the microscopic model is verified by experiments.