The formation mechanism of subsurface damage of sapphire materials was introduced. In consideration of the boron carbide abrasives with advantage of smaller subsurface damage, the subsurface damage of a sapphire crystal after lapping by boron carbide abrasives with different particle sizes was studied based on the loose abrasive lapping method. The lapped sapphire wafer was etched by KOH chemical corrosion processing technology, the subsurface damage morphology of the sapphire crystal was indirectly reflected by specific etch pitimage and the subsurface damage depths were achieved with gritparticle sizes W20, W10 and W5 by loose boron carbide abrasive lapping. The subsurface damage morphology, surface roughness and etching rate of the sapphire crystal at different etching time were obtained also. The results show that the subsurface damage density of sapphire crystal lapped by loose boron carbide abrasive is remarkable, but the damage depth is lower, and it increases with of the abrasive sizes. After lapping by looseboron carbide abrasives with gritparticle sizes of W20, W10 and W5, the depths of subsurface damage are 7.4, 4.1 and 2.9 μm, respectively, which is about 1/2 of the size of abrasive. It indicates that the lapping method with boron carbide abrasives is beneficial to the reduction of subsurface damage of the sapphire. In addition, the sapphire wafer with low subsurface damage can be achieved quickly by lapping methods with abrasive particle sizes from larger to smaller.