In order to explore the relationship between single crystal sapphire subsurface damage depth and polishing parameters of cluster magnetorheological finishing, a relationship model of the subsurface damage depth and the polishing parameters was established. The influence of the polishing parameters on the subsurface damage depth was studied, the relation model was verified by orthogonal experiments. White light interferometer was used as the measuring tool, α-Al2O3 was used as the polishing liquid, and three levels were selected for each experimental factor in the experiment. The experimental results show that the subsurface damage depth is related to abrasives size and polishing pressure, the subsurface damage depth increases with the increase of the polishing pressure and the abrasives size .The effect of the polishing pressure on the subsurface damage depth is much greater than that of the abrasives size. When the polishing pressure and the abrasives size are 25 kg and 280 nm, the minimum subsurface damage depth reach 0.9 nm after 100 minutes polishing, the polishing pressure is the main factor affecting the subsurface damage depth in cluster magnetorheological finishing. Under the current experimental conditions, the subsurface damage can be quickly removed when the polishing pressure is 25 kg.