The invention discloses a clamping piece for plate lifting of a building tower crane. The clamping piece comprises a first supporting block, a second supporting block, a third supporting block and a fourth supporting block. Supporting beams are rotationally hinged on the right side of the front end face of the first supporting block, the rear side of the right end face of the second supporting block, the front side of the left end face of the second supporting block and the right side of the rear end face of the fourth supporting block, and spliced holes are formed in the tip ends of the foursupporting beams on the vertical direction. Clamping plates are fixed welded on the rear side of the left end face of the first supporting block, the left side of the front end face of the second supporting block, the right side of the rear end face of the third supporting block and the front side of the right end face of the fourth supporting block, and adapting holes are formed in the four clamping plate in the vertical direction. The supporting beams are clamped with the clamping plate and are spliced and penetrate through the splicing holes and the adapting holes in a sliding mode. the clamping piece is convenient to adjust the distance between the adjacent supporting blocks to be matched with the section size of the plate, is convenient for lifting and discharging, and is simple and practical.