A composite cooling fan includes a frame, a fan blade and a lateral valve. The frame has an air hole penetrating the frame and a lateral air outlet locating on one side of the frame and connecting with the air hole. The fan blade is disposed in the air hole and includes an impeller, multiple axial blades surrounding the impeller and multiple centrifugal blades surrounding the axial blades. The lateral valve is disposed on the lateral air outlet and includes a valve stem and a switch baffle linked with the valve stem. The valve stem is used for making the switch baffle at the lateral air outlet open or close.