Optimizing manufacturing process modeling is critical to improving the efficiency and quality of manufacturing. However, manufacturing processes in general can be very complicated. A manufacturing process may involve (a) transforming a material into a new form, (b) combining different materials to form a new object, and (c) retrieving a certain part from a material as a new entity. All those activities could be confusing because many intermediate objects that exist only for a short period during the manufacturing process may have no formal names. To solve this problem, this paper proposes that composition trees (CT) can be successfully used to model manufacturing processes. Composition trees are parts of the formal notation in behavior engineering (BE), which is an innovative approach to the development of large software systems. For a composition tree, its characteristics of being intuitive, expressive and formal give it many advantages over other formal and informal modeling languages in software engineering. This paper uses a cooking case study to demonstrate how to use a composition tree model manufacturing processes. It is argued that the method could be applied to process engineering to good effect.