The invention relates to a good-stability clamping device. The clamping device comprises clamping jaws, a jaw cavity, clamping jaw installation plates, connection rods, a push block and a cylinder. A piston rod of the cylinder and the lower end of the push block are fixed. The two connection rods are hinged to the left end and the right end of the push block through connection rod pins correspondingly. The other ends of the two connection rods are hinged to the two clamping jaws correspondingly. The jaw cavity is fixed to the upper end of the cylinder. The two clamping jaw installation plates are fixed to the upper portions of the front inner wall and the rear inner wall of the jaw cavity correspondingly and extend out of the upper end of the jaw cavity. The middle lower portions of the two clamping jaws are hinged between the two clamping jaw installation plates through clamping jaw pins correspondingly in a spaced mode. A spring piece is further fixed between the two clamping jaws through an installation pin. According to the clamping device, clamping heads are easy to replace, and usage is convenient.