Traditional Chinese medicine (TCM) theory is an experience-dependent theory. It interprets concepts by making analogy in metaphorical terms, that is, it explains new concepts with the knowledge people have already knew. This paper discussed how the ancients created the metaphors of wood by its natural attributes, drew analogies to introduce wood-shaped persons and the TCM concepts of physiology, functions, pathology, diagnosis and treatment by a metaphor cognition system taking wood as a source domain.