The invention provides a damping device for a liquid storing tank. The damping device comprises a damping cylinder with the hollow interior. The first end of the damping cylinder is an opening end. The second end of the damping cylinder is a closed end. The first end of the damping cylinder can communicate with the interior of the liquid storing tank through a through hole in the tank wall of theliquid storing tank. A damping piston capable of sliding in the axial direction of the damping cylinder in a reciprocating manner is arranged in the damping cylinder. The periphery face of the dampingpiston is attached to the inner wall of the damping cylinder in a sealed manner. An elastic element capable of telescoping in the axial direction of the damping cylinder is arranged between the innerside end face of the second end of the damping cylinder and the damping piston. The two ends of the elastic element are connected with the inner side end face of the second end of the damping cylinder and the damping piston correspondingly. According to the damping device for the liquid storing tank, in the using process, the damping device communicates with the interior of the liquid storing tank through the through hole in the bottom of the liquid storing tank, by means of reciprocating vibration of the elastic element of the damping piston arranged in the damping cylinder, impact on the tank wall of the liquid storing tank by liquid can be effectively dissipated, the buffering and damping effects are achieved, and the safety and the service life of the liquid storing tank are ensured.