The invention discloses a film patching mechanism of an abnormal-shaped window patching machine. The film patching mechanism comprises a machine frame. The machine frame is provided with a conveying channel for conveying paper boards. The conveying channel is provided with a paper board positioning device and a film patching mechanism for carrying out film patching on the paper boards. The paper board positioning device comprises a front lay positioning device for front-back position positioning of the paper boards and a side lay positioning device for left-right position positioning of the paper boards. The front lay positioning device is arranged over the conveying channel through a transverse rod, and the side lay positioning device is arranged on the side of the conveying channel. The film patching mechanism comprises a placement channel where patching films are placed and a film suction pressing device used for enabling the films on the placement channel to be attached to the conveying channel. The film suction pressing device comprises a suction cup and a driving mechanism. The driving mechanism drives the suction cup to be rotated between the placement channel and the conveying channel to press the films to the paper boards, and the films can be rapidly and accurately attached to the paper boards.