The invention discloses a water-jetting gun. The water-jetting gun comprises a gun body, a nozzle, a handle and an opening and closing device, wherein the gun body comprises a grasping part and a gun barrel positioned on the upper part of the grasping part, and the grasping part and the gun barrel are both in hollow states and communicated to form a water flow passage; the nozzle is arranged on the front end of the gun barrel; the handle is pivotally connected with the grasping part in the side direction of the grasping part; the opening and closing device comprises an opening and closing rod arranged in the gun barrel in a penetrating way, the opening and closing rod comprises a main body and an outer diameter reduced part positioned in the main body, the rear end of the opening and closing rod penetrates through the gun barrel to be fixed with the upper end of the handle and can be driven by the handle to move towards a rear side, and the opening and closing rod is provided with a restoring spring capable of enabling the opening and closing rod to move towards a front side; the rear end surface of the nozzle is provided with a water outlet hole used for being penetrated by the opening and closing rod, when the opening and closing rod is positioned on an initial position, the water outlet hole is closed by the main body, and when the outer diameter reduced part of the opening and closing rod moves towards the rear side to the water outlet hole, the water flow passage is communicated with the inside of the nozzle through the water outlet hole. The water-jetting gun has simple structure and convenience for operation.