To investigate the material removal mechanism and the subsurface damage evolution of monocrystalline gallium oxide， a systematic study was conducted by experimental methods. Firstly， the variable-depth nano-scratching test was used to simulate the material removal process of single grit and explore the material removal mechanism in the grinding process. Subsequently， the diamond grinding wheels with mesh sizes of SD600， SD1500， and SD5000 were used to carry out the grinding tests on the monocrystalline gallium oxide and to analyze the morphology of the ground surface and the evolution of subsurface damage. Scanning electron microscope and transmission electron microscope were used as the primary means of characterization， and the stress distribution during the scratching process was analyzed with the finite element method. The results indicate that the cross-acting slip band with multi-directions may lead to irregular fracture pits， and the orientation cracks were greatly affected by the （-3-10） plane of the monocrystalline gallium oxide. The grinding experiments reveal that the ground morphology， characterized by a brittle removal surface dominated by fracture pits and orientation cracks， gradually evolved into a completely plastic removal surface with the decrease of mesh sizes.