In this paper, a system based on successive image analysis is proposed for periodic measurement of flank wear in milling. The successive images are captured while the spindle is rotating. The blur of the moving images is minimized by the use of a high-speed camera and low spindle speed during the image capture. A method based on image series to measure flank wear has been developed and successfully applied on these moving images. Its performance is compared with the method based on individual still or static images. The results show improved robustness of this system with high potential for industrial application to measure the flank wear in-cycle (between passes) without stopping the spindle.