Single sapphire crystal is an important optical element and semiconductor substrate material, widely used in industry, national defense and scientific research, etc. But, high hardness and good chemical stability of the sapphire make it hard to be polished by applying mechanical chemical polishing and other contact methods. Therefore, laser polishing will be one of polishing methods which are supposed to replace contact method polishing sapphire. This essay, based on the summary of the study on laser polishing mechanism and technique of processing sapphire by laser, from the perspective of the interaction mechanism of the laser and the substance, analyzes in theory the interaction of laser and sapphire during the sapphire is polished by the short-wavelength laser. Experiments proved that under the cases of 20mJ and 40mJ laser energy when green laser polishes sapphire, the main material removal mechanism is fracture, at the same time, light melt mechanism exists.