The invention discloses a swing-cylinder hydraulic motor which comprises a shell and a shell cover, wherein the side edge of the shell cover is provided with an oil flowing disc and an oil distribution disc; a first concave hole and a second concave hole are respectively arranged in the shell and the shell cover; two ends of a swing cylinder are respectively provided with a first shaft end and a second shaft end; the first shaft end and the second shaft end are both penetratively arranged in the first concave hole and the second concave hole; the end part of the oil distribution disc is provided with an annular groove; the bottom of a constricting groove of the annular groove is provided with an O-shaped seal ring, a seal ring and a gasket; the oil distribution disc is provided with a first oil chamber and a second oil chamber; the first oil chamber and the second oil chamber are both of a groove; the end surface of the oil distribution disc and the lateral wall of the first oil chamber are provided with an arc-shaped transitional surface respectively; and the end surface of the oil distribution disc and the lateral wall of the second oil chamber are both provided with an arc-shaped transitional surface. In the invention, an oil-sealed transitional belt is combined with the arc-shaped transitional surfaces so that the oil flowing area is gradually changed, therefore the vibration noise is reduced, and the service life of the oil distribution disc can be prolonged at the same time.