The invention provides an automatic polishing system for stainless-steel cups, which comprises a conveying mechanism, a feeding mechanism and an external polishing mechanism, wherein the conveying mechanism comprises a conveying frame, a conveying table unit and a pressing unit; the conveying table unit and the pressing unit are mounted on the conveying frame; the feeding mechanism is mounted on a bracket faceplate of the conveying mechanism and comprises a feeding frame and a motion control unit mounted on the feeding frame; the external polishing mechanism comprises a polishing frame, an abrasive belt control unit and a part motion control unit; and the abrasive belt control unit and the part motion control unit are mounted on the polishing frame. The automatic polishing system for the stainless-steel cups can completely replace manual operation, remarkably improves the working efficiency, lowers the labor cost and increases the automation level of enterprises. Meanwhile, the automatic polishing system for the stainless-steel cups realize accurate control of polishing parameters and can achieve more stable and favorable polishing quality.