For improving bullet productivity, the rotor-styled high-speed exact dynamic bullet size measuring system is designed, which uses 12 work place high-speed rotor model and modern scatheless measure control technology based on the technics and specialty of on-line high-speed bullet size measuring. This paper introduces the system design theory, system model and control system design technique. It also uses the means to deal with all kinds of signals collected on -line, such as compensating displacement, filter arithmetic, etc ,which were approved in sample machine. The experiment indicates that the system satisfies need of measuring 200 bullets per minute and 0.01mm precision, greatly exceeding domestic measuring efficiency of 80 bullets per minute.