The invention discloses a pumping blowdown device which is characterized by comprising a piston cylinder, a shell base and a piston cylinder cover. The device is characterized by further comprising an overflow locking mechanism, and an adjustable exhaust mechanism, wherein the overflow locking mechanism comprises an overflow suction disk which is disposed on the bottom of the piston cylinder by a fixation part; and the adjustable exhaust mechanism comprises an exhaust adjustment valve and a valve base, one end of the exhaust adjustment valve is opened to form a row of air grooves, multiple exhaust holes are formed in the exhaust adjustment valve, the valve base is disposed on the piston cover, and the exhaust adjustment valve is moved with driving of a piston. According to the invention, pumping effects of the pumping blowdown device are greatly improved; and the problems in the prior art that pumping effects are greatly reduced and complete pumping cannot be achieved as complete adhesion between the piston cylinder end face and the shell base inner wall end face cannot be guaranteed, and a pumping speed of the piston cannot be controlled to approach a washing speed of a toilet can be solved, so that use and promotion of the products are improved.