In production, if the tow used in cigarette has the edge rolling problem, it will have an effect on the quality of production. Consequently, finding out the rolling tow has become one of the urgent problems and has important significance.According to the feature of crimping tow, gray the G component of RGB image and use Roberts operator to deal with the edge rolling tow from the view of image processing. And combine with binarization, filtering and other methods to simulate and calculate the width of tow exactly to judge whether the tow is crimping. Compared with classical Roberts operator, the improved operator detects more accurately and also meets the need of system. Solidify the algorithm to the system of hardware, the issue has been solved by the system and it can detect the tow online. The result indicates that the operator can detect the crimping tow well, accurately and efficiently.