Abstract: Immersive virtual assembly, a man-in-loop virtual reality system, can be used for the design and assembly of large equipment, personnel training and other fields. As one of its key technologies, how to realize “real” man operating on “virtual” objects is still a challenging task. In this paper, an interaction feature modeling method based on interactive zone and finite state machine (FSM) is proposed. Interactive zone is the visual representation of the interaction process. Different settings of interactive zone lead to different interaction monitoring functions. The possible interactions between user and object depend on object’s binding zones. Virtual objects can understand the intention of user’s action through the interactive zone, and then transit their interactive state according to the related FSM. The state of objects determines the action that user can take. According to the current state, the object will provide effective operational clues to guide the user to interact with them correctly. On that basis, task-level process control is proposed to manage the assembly process. Last but not least, direct hand interaction and indirect interaction using tools can be handled in the same way through the probe zone. This method has good versatility, extendibility and reusability of interaction process. The effectiveness is verified through the application of actual projects.