A tool for clamping using end surfaces of box workpieces, comprises a soleplate and an upper template. A tightening cylinder has a piston rod connected with a top plate, and the top plate and the piston rods are in swinging connection. Three protrusions are arranged on the upper surface of the top plate and distributed in a triangle shape. A rotating shaft is arranged beside a position of the upper template, the upper end of the rotating shaft is provided with a hand wheel capable of driving the rotating shaft to rotate, the rotating shaft is sleeved with a compression spring on the portion between the hand wheel and the upper surface of the upper template, and the lower end of the rotating shaft is fixed with one end of a transverse support rod which is linked with the rotating shaft.