Compared with contact measurement, machine vision inspection, a noncontact measurement, has the advantages of high efficiency, complete information, good stability, and recognizable defects. It has been used increasingly in the field of gear inspection. Many gear inspection instruments based on machine vision technology have been developed in the last 10 years, including video measuring machines, flash measuring machines, CVGM instruments, and online inspection equipments that can perform both comprehensive gear inspection and analytical gear measurement. This paper examines the development processes and characteristics of gear visual inspection instruments; analyzes the research and application progress of algorithms such as edge detection, subpixel positioning, feature extraction, and pattern recognition in gear visual inspection; summarizes the technical development of machine vision in gear accuracy measurement and gear defect inspection; and identifies the future development prospects of gear visual inspection instruments and technology.