Abstract: With the increasing demand of requirement for the quality of raw materials in industry, surface defect inspection of steel bar became an essential part of industrial production. Surface defect inspection technology mainly included traditional NDT and machine vision detection method, and the later was more and more widely used because of its rapidity and high accuracy. The characteristics of vision-based detection technology for steel bar surface defect and the newest research development were introduced. The working principle of vision inspection technology and key issues were analyzed. It was proposed that advanced technology both in home and abroad should be actively absorbed and innovations be then made to promote the development of machine vision inspection technology.