Machine vision, a cross-sciences discipline, has a wide application field. In recent years, with the innovation in theory and the development in technology, machine vision has developed so fleetly. The development status of machine vision's key techniques have been explained in detail, such as illuminating source, optical lens, camera, image acquirement, signal processing, executive framework, and so on. The technique of machine vision has found increasingly wide applications in many industrial fields. The applications in the following three fields (automatic inspection, intelligent assemblage and visual servo) are presented.