The invention relates to the technical field of auxiliary devices, especially to a water leakage prevention device in hysteroscopy. The device includes a hysteroscope, the upper part of which is connected with a leakage-proof device; one end of the leakage-proof device is connected with a gas injection device; the leakage-proof device comprises a gas bag, two ends of which are connected with sleeve columns; sealing rings are connected to the inner sides of the outer ends of the sleeve columns; the gas injection device comprises a gas injection column, the inner side of which is provided with aspring; one end of the spring is provided with a base plate; a limiting plate is disposed on one side of the base plate; and one end of the gas injection column is connected with a limiting cap. By inflating at a breather pipe, the gas bag is expanded to compact a gap between an endoscope sheath and the cervix uteri, water leakage is avoided, and an operation can be performed smoothly. When an injector is used for gas injection, the limiting plate is arranged to block a cap hole of the limiting cap under the action of the spring, and then air leakage is avoided. During inflating, the limitingplate only needs to be ejected open by the injector, and then the air bag can be inflated to expand.