The invention discloses a construction method for rapidly mounting an ALC plate. The construction method comprises the steps that the ALC plate is pretreated, the ALC plate is horizontally placed in a feeding area of a mounting machine, the posture of the ALC plate is adjusted, the ALC plate is mounted, and a hoisting frame is separated from a hoisting piece. The mounting machine comprises a frame and a machine frame, the frame comprises a head, a tail and a plurality of body units arranged between the head and the tail, and the head, the body units and the tail are detachably spliced in sequence; and the machine frame is detachably connected to the upper end face of the front end of the head. By the adoption of the technical scheme, the mounting machine can achieve the function of mounting the ALC plate in a narrow terrain or an area where the mounting machine cannot easily pass through in the mode that single parts are transported in place and then assembled on site. When the ALC plate is pulled, one end of the ALC plate is lifted up and slowly inclines upwards, meanwhile, the single side face of the ALC plate gradually gets close to a building structure, the single side face and the edge of the ALC plate are not blocked by connecting pieces, the ALC plate can be attached to the building structure more easily, and mounting and locking are convenient.