The utility model discloses an online copper pipe flaw ink mark detection device, which comprises a flaw detector, an ink jetting device, an ink mark detection device, a distance measurement device and a control device, wherein the flaw detector is used for carrying out online detection on flaws; the ink jetting device is used for jetting ink to flaws detected by the flaw detector; the ink mark detection device is used for detecting the color and the area of the ink mark jetted by the ink jetting device; the distance measurement device is used for measuring the walking length of a copper pipe; the input end of the control device is connected with the output end of the distance measurement device; and the control end of the control device is connected with the ink jetting device and the ink mark detection device. The utility model prevents products the colors and the ink jet area of which do not meet the demands from being transferred to the next process, and thereby, the generation number of the unqualified products is reduced.