Abstract: Chemical effect of polishing slurry and rotational speed are very important for Material Removal Rate(MRR) and surface quality during polishing. Under different rotational speed, the slurries with different pH were used for the analysis of spinel wafers lapping, and the effects of pH slurries on MRR and surface quality were explored. Through making the slurries with different pH, both groups of experiments were carried out of chemical mechanical polishing(CMP) at the speeds of 80 r/min and 100 r/min. The MRRs of spinel were measured using the lost weight analysis law, and the surface roughness was checked with a roughness instrument. They were used to analyze the effects of pH and rotational speed on lapping accuracy, and were also used to explore the mechanism of CMP. The results show that the MRRs increase with the rising of acid or alkaline, and that their roughness decreases instead. Of them, alkaline slurries have a greater effect on MRR and roughness. With the increase of rotational speed, MRR and surface roughness can also be increased obviously. A suitable speed should be considered carefully. The study will lay an experimental foundation for exploring further the chemical mechanical polishing mechanism.