Book of Changes accommodates heave, earth and human, while the soul of Chinese medicine is harmony of heaven, earth and human. The theories of Yin-yang and five phases were described in Canon of Medicine and they are derived from the ideas in Book of Changes. The essences of Book of Changes and Canon of Medicine were inherited in Treatise on Exogenous Febrile Diseases. It is considered that Chinese Medicine and Book of Changes share the same origin from the analysis of Sini decoction, six-meridian syndrome differentiation and autobiographic note of Treatise on Exogenous Febrile Diseases.