The invention provides a high-efficiency water decanter which comprises a buoy and a water discharge pipe, wherein the water discharge pipe is fixedly connected with a water discharge hole arranged at one side of the buoy; the buoy is connected to two slide rails which are transversely arranged through sliding chutes, arc-shaped guide rails are arranged in the front and at the rear of the buoy, and the arc-shaped guide rails are connected with gravity blocks; a plurality of grids are uniformly arranged in the buoy, and filter media are arranged in the grids; the water discharge hole is provided with a filter screen. The high-efficiency water decanter provided by the invention has the advantages of uniformity stress, high-efficiency water discharge and low cost.