X-ray supermirror is a non-periodic multilayer structure, whose optical performance is greatly affected by the stability and accuracy of the deposition rate in the fabrication using the direct current (DC) magnetron sputtering. By considering the location-setting time of the substrate positioning above the sputtering target, the deposition rate can be accurately determined. Experimental results show that the optical performance of the supermirror is in agreement with the design aim, which indicates that the layer thickness is well controlled and coincides with the desired ones.