The tablet cores(micro-pills, small pills or plain tablets) make continuous and complicated orbital motion within a closed rotating drum under the action of a streamline guide plate. Controlled by computer and according to the optimum technological parameters, they are automatically sprayed with coating medium while hot air under a negative pressure is led in from one side of an air distributing pipe in the center of the drum, then the clean hot air penetrates through the tablet core layers and is discharged after being collected to the other side of the air distributing pipe by a pore duckbill-shaped (or oval) air paddle embedded in the tablet core layers, so that the coating medium sprayed on the surface of tablet cores will dry rapidly and evenly, thereby forming a layer of solid, compact, neat and smooth surface film.