Dishui Lake is a large man-made freshwater lake at Nanhui Beach in the Changjiang Estuary. The inflows/outflows driven by rivers, the thermohaline circulation, the wind-driven circulation, and the combined circulation in the Dishui Lake in summer driven by the above three dynamic factors were simulated by using improved ECOM model. The inflows/outflows driven by river appear mostly on the line between the inlet and outlet of rivers, generating eddy in the lake. Two cyclonic eddies appear in the thermohaline circulation induced by the heating of surface water in the lake. The east one of the two cyclonic eddies has wider area than the west one, and the speed at the middle and bottom layers is smaller. The surface winddriven currents at the center of the lake mostly meander and northwestward flow. There exist eddies at a side of the strong meander. Due to the mass conservation, the reversed compensation currents appear at the bottom layer. The combined surface currents flow northwestward flow, while the bottom compensation currents flow southeastward. The combined circulation is mainly driven by the wind. The inflows/outflows in the combined circulation appear at the middle and bottom layer due to the against wind.