High efficiency and precision grinding of monocrystalline silicon plays an important role in the field of microelectronics and optoelectronics manufacturing. To explore the cutting characteristics and mechanism of precision grinding of silicon wafer devices, diamond grain with triangular pyramid shape was used to scratch the surface of monocrystalline silicon under different loading pressures to simulate the grinding process. The evolution law of scratch morphology, cutting force and cutting depth were analyzed, and the micro cutting mechanism of monocrystalline silicon was explained. The critical value of microcracking removal is normal cutting force of 80 mN and critical cutting depth of 2.03 μm. The critical condition of spalling removal is normal cutting force of 800 mN and cutting depth of 5.65 μm. Cutting depth and grinding force ratio have distinct differentiation characteristics under different cutting mechanism conditions. The variation law of average cutting depth with loading pressure shows self similarity characteristics. In addition, the cutting force equations of plastic removal, micro crushing removal and spalling removal are constructed respectively, which can more accurately describe the close relationship between cutting force and cutting depth. These works are of great significance to further improve the cutting theory of monocrystalline silicon materials, and improve the manufacturing ability of semiconductor.