The present invention discloses a constant-pressure and adjustable discharge system for endoscopic surgery. The constant-pressure and adjustable discharge system for the endoscopic surgery comprises an aspirator, an adjusting tube, a waste liquid collecting bottle and a pressure adjusting bottle, liquid is arranged in the pressure adjusting bottle, an upper end of the adjusting tube communicates with one end of an upper side of the waste liquid collecting bottle, the other end of the upper side of the waste liquid collecting bottle communicates with the aspirator, a lower end of the adjustingtube extends into the pressure adjusting bottle, an upper side of the pressure adjusting bottle is provided with a negative pressure interface, the liquid in the pressure adjusting bottle is relatively movable with the adjusting tube, and an air venting valve communicating inside and outside is arranged on the pressure adjusting bottle. Active suction and passive discharge can be freely converted;a discharge speed and an intra-abdominal pressure are stable, operators can conduct convenient and visual adjustment, thus the constant-pressure and adjustable discharge system greatly compensates shortcomings of existing aspirators in the endoscopic surgery and is more convenient and secure.