The invention discloses a door window plastering and shaping device and method. The door window plastering and shaping device comprises four supporting structures with same structures. Each supportingstructure is supported at one corner of a door window opening. Each supporting structure comprises a first supporting plate and a second supporting plate, wherein the first supporting plate and the second supporting plate are in hinged connection. The widths of the first supporting plates and the second supporting plates are greater than or equal to the thickness of a wall. An inserting hole is formed in the end part of each first supporting plate. A telescopic mechanism is arranged at the end part of each second supporting plate. The telescopic mechanism of one of the second supporting plates in the adjacent supporting structures is matched with the inserting hole of another first supporting plate to be used, so that the adjacent supporting mechanisms are connected. According to the doorwindow plastering and shaping device, through the four supporting structures which can be in head-to-tail connection with one another, the door window opening is fixed, and transporting and operatingare convenient; and the telescopic mechanisms are arranged, so that the door window plastering and shaping device can be applied to different door window openings, adjusting is facilitated, the applicability is improved, and the cost is saved.