The tablet cores to be film coated make continuous complicated orbital motion within the closed rotating drum under the action of a streamline guide plate. During the motion, coating medium automatically sprays according to the technological process and rational technological parameters, at the same time hot air is supplied under a negative pressure. The hot air penetrates through the tablet core layers and is discharged form the bottom of the layers, so that the coating medium sprayed on the surface of tablet cores will dry rapidly and evenly, thus forming a solid and smooth surface film.