Abstract: Surface physical damage detection is an important part of the shaft part quality inspection. In order to improve the automation level of the quality detection of shaft part and establish its relevant industry quality standard, a machine vision inspection system connected with MCU was designed to realize the surface detection of shaft part. The system adopted the monochrome line-scan digital camera and used the dark-field and forward illumination technology to acquire images with high contrast; the images were segmented to Bi-value images through maximum between-cluster variance method after image filtering and image enhancing; then the mainly contours were extracted based on the evaluation criterion of the aspect ratio and the area; then the coordinates of the center of gravity of defects area, namely locating point coordinates were calculated. At last, locations of the defects area were marked by the coding pen communicated with MCU. Experiment showed that no defect was omitted and false alarm error rate was lower than 5%, which showed that the designed system met the demand of shaft part on-line real-time detection.