This paper presents a new method for autonomous computer aided process planning (A-CAPP) in intelligent manufacturing system, in which the related input and output of the system are discussed on the basis of comparative analysis of traditional CAPP. The crucial functional components of the A-CAPP system, such as event scheduling management, manufacturing process planning, operation process/step planning, numerical control machining program planning, process simulation and evaluation, are introduced; and the methods of process knowledge management, including process feature knowledge, manufacturing resource knowledge and process method knowledge, are discussed as well. A-CAPP applied for intelligent manufacturing system can effectively support the production line reconstruction dynamically; shorten the time of production line configuration modification in accordance with customers’ requirement change or market requirement fluctuation, and further more to balance the production lines load.