Lots of lapping experiments were carried out for a single crystal sapphire by using a diamond fixed abrasive (FA) pad. The effects of different kinds of slurries on Material Removal Rate(MRR) and the surface quality of a workpiece were studied. The chemical influences of slurries on the surface of the crystal sapphire were analyzed and the material removal mechanism of the sapphire crystal by fixed abrasives was explored. Experiments show when W14 diamond fixed abrasive plated nickel is used to lap the single crystal sapphire and the deionized water is used as slurry, the MRR is 149.8 nm/min, and the surface roughness (Ra ) is 76.2 nm. However, after adding 2% of ethylene glycol into the slurry, those are 224.1 nm/min and 50.7 nm, respectively. A photoelectron spectrometer (XPS) was used to analyze the surface of the workpiece, and it shows that the solution of ethylene glycol has more chemistry promotion for the sapphire surface. These results indicate that the addition of ethylene glycol is helpful for the formation of softened surface layer on the sapphire surface and increases the activity of sapphire surface. It means that the slurry plays an important role for enhancing lapping efficiency and improving surface quality of workpieces.