The mechanism of nano-grinding of single crystal silicon carbide （SiC） with lattice defects remains unclear. A molecular dynamics simulation system is used to study the nano-scratching mechanism of single crystal SiC with lattice defects. The simulation model including diamond abrasive grains and 4H-SiC workpieces with different lattice defects is built. The molecular dynamics simulation results reveal the effects of different defect types on key parameters such as interatomic potential energy， temperature， stress and machining performance. It is found that vacancy defects lead to instability in the interatomic potential energy of the workpiece， which in turn results in increasing the temperature of the workpiece up to 671 K after scribing， while dislocation defects show relative stability. During nano-scratching， crystals with dislocation defects exhibit the highest average paradigm equivalent stress of 5.29 GPa， while crystals with vacancy defects exhibit the lowest stress of 5.07 GPa， which suggests that vacancy defects reduce the yield strength and favour the removal of atoms， whereas dislocation defects increase the yield strength and impede the removal of atoms. Furthermore， vacancy defects inhibited dislocation nucleation and reduced the thickness of the damage layer， whereas dislocation defects led to significant dislocation formation and a deeper damage layer.