The invention provides a leakage-free hydraulic buffering vacuum breaker valve. According to the vacuum breaker valve, a hydraulic cylinder and the valve plate are arranged, wherein the hydraulic cylinder is installed on the valve plate and acts together with the valve plate, a sliding seal between the bottom of the hydraulic cylinder and a valve rod is located inside a hydraulic buffering cavity,so that complete sealing in the hydraulic cylinder is guaranteed, hydraulic buffer oil is in a completely sealed state, sealing abrasion leakage is avoided, and the service life of the vacuum breakervalve is prolonged; moreover, a throttling valve is arranged, the buffering effect of the valve plate in the closing position is improved, noise generated through collision of the valve plate and a valve seat is reduced, a supporting sleeve plays a role in supporting the hydraulic cylinder, and further balances radial force of opening and closing of the valve plate so as to prolong the fatigue life of the vacuum breaker valve, meanwhile, a spring is arranged, so that axial force is balanced; and in addition, the vacuum breaker valve is simple in structure, reasonable in design, safe and reliable, and potential safety hazards during operation of a water turbine are effectively reduced.