A buoyant dynamic ornament includes a water storage tank, a transparent buoyant tank, a plurality of floats, and a water level control. By the water level control, the water flowing in and out the water storage tank and the buoyant tank is controlled and the water level varies so as to provide the floats buoyancy. Thus the floats rise or sink according to the variation of water level. At the same time, the figures or light on the floats also moves up and down. The dynamic decorative effect is achieved.