Abstract: To improve the lapping efficiency and processing quality of the sapphire substrate, two lapping plates composed of vitrified bond diamond lapping pellets with different hardness were developed, and the lapping process experiment was carried out on the sapphire substrate to evaluate its lapping performance. The results showed that as the processing time increases, the material removal rate (R_MRR) and surface roughness (R_a) of two lapping plates both gradually decreased and finally stabilized. With the increase of the rotation of the plate speed, the material removal rate of the two plates first increased and then decreased, when the rotation speed of the plate was 60 r/min, the maximum material removal rates were 1.81 μm/min and 1.27 μm/min, respectively, but the surface roughness continued to decrease. As the lapping pressure increased, the material removal rate of the two plates continued to increase, when the lapping pressure was 34.5 kPa, the maximum of material removal rate reached 2.03 μm/min and 1.49 μm/min, respectively, the minimum of surface roughness were 0.165 μm and 0.141 μm, respectively. Comparing the wear performance of the two lapping plates with different hardnesses, it can be found that the higher the hardness of the lapping plate, the higher the material removal efficiency and the higher the grinding loss ratio of the plate, but the surface roughness of the workpiece was higher.