A novel overprint marks suitable for both human eyes and digital images was designed based on conventional cross registering mark and registering circle marks. The images of the register marks were collected by CCD components. The images were pretreated and segmented. The coordinates of the four colors circle centre and the parameters for overprint deviation were determined after digital image processing and image segmentation. The results showed that the homocentric circles in register marks can avoid overlapping between four colors in image segmentation; the method possesses much higher precision with overprint deviation less than 0.04 mm in case of image resolution above 300 dpi. Meantime, it owns fast recognition, which can satisfy the requirement of detecting overprint marks on line.