With the development of national defense military and LED industry, the demand for sapphire substrates and the complexity of their shapes is increasing. Traditional polishing methods such as chemical mechanical polishing has the deficiencies of low efficiency and poor cambered-surface processing effect, while bonnet polishing, as one of the rapid polishing methods, is applicable to a variety of cambered surface polishing. Therefore, the bonnet polishing technology was applied to sapphire cambered-surface polishing. Firstly, the polishing motion model of sapphire was established on a robotic platform and the optimum processing parameters were obtained through single-factor test and orthogonal test. Then the polishing for the whole cambered surface was carried out under the optimum parameters and the effect of polishing time on the surface quality was investigated. The results show that the surface roughness Ra of the cambered surface reduces from 541.5 nm to 41.2 nm and the workpiece is conformal when the polishing time is 8 min, which verifies the feasibility of bonnet polishing for sapphire cambered surface.