Aiming at the problem of poor automation and low level of information integration in the on-line assembly control system of traditional mechanical products, this paper establishes an online quality control system based on machine vision. Firstly, the whole conceptual model of V-OQCS is established, the structure of machine vision is introduced, and then the visual factor library of the online assembly quality control system is established. At last, taking a gearbox assembly system as the research object, of the V-OQCS application is developed to verify the feasibility and effectiveness of the proposed method.