The invention provides a high-efficiency water turbine. The water turbine comprises a pump shell, the pump shell comprises an upper end cover, a lower end cover, a first transition connecting plate, asecond transition connecting plate, a front side plate and a rear side plate, the upper end cover and the lower end cover are connected, a stator and a rotor are arranged in the pump shell, the crosssection of a stator is an oblateness, a fixed shaft penetrating through the stator is fixedly connected with the front side plate or rear side plate, the rotor comprises a front round plate, a rear round plate and a blade plate connected between the front round plate and the rear round plate, the inner edge of the blade plate can be in clearance fit with the upper end arc face and the lower end arc face of the stator, water inlet and outlet of the inner edge and the outer edge of the blade plate have the time difference, the front or rear round plate is located on the gap between the front orrear end face of the stator and the front or rear side plate, the two round plates are connected with the fixed shaft through bearings, the rear or front round plate is fixedly connected with a poweroutput shaft, the inner surface of the power output shaft is connected with the fixed shaft through a bearing, the outer surface of the power output shaft is connected with the rear or front side plate through a bearing, a water inlet is formed in the transition connecting plate opposite to the opening direction of the blade plate, and an air exhaust channel and an air inlet channel are formed inthe positions, close to the water inlet and the water outlet, of the upper end cover. The water turbine is simple in structure, low in manufacturing cost and capable of filling up the model selectionblank of a head water turbine.