The present invention is an electropolishing process and device for electropolishing an inner surface of a long tube, especially applied to a long tube of greater than two meters and a diameter range between 0.3 and 5 cm. Wherein, the present invention comprises at least one tube, and one complex electrode. An inner surface of the tube is for electropolishing process, and it is an anode as well. The electrode is a cathode and placed on a center of a partition. An end of electrode connects to a cable, the cable is driven by an axial mechanism to be moved the electrode toward the axial mechanism itself. Inside of the tube is full o electrolyte, which is an electrifying medium to connect both anode and cathode. Further, electrolyte cooperates with the electrode to perform the electropolishing process on the inner surface of tube.