Voltage flicker is defined as "the impression of unsteadiness of visual sensation induced by a light stimulus whose luminance or spectral distribution fluctuates with time" according to IEC standard. And it is also known as voltage fluctuation, light flicker, and flicker. In Korea, the equivalent 10Hz voltage flicker index has been used as the standard index. But now we are faced with the change into the new standard for flicker because U.S.A and many advanced European countries adopted the IEC 61000 standard as a criterion of voltage flicker. This paper introduces the digital flicker measuring algorithm based on IEC 61000-4-15 in detail and new approach for our unique distribution system.