In this study, the author researched the process in which the philosophical basis of 'Sa Sang Medicine (四象醫學)' and its methodology build up the principles of Sa Sang Medicine, and then, examined how the principles were applied to the theoretical system of Sa Sang Medicine. The conclusion would be summarized as follows. 1. 'Nae Kyung Medicine (內經醫學)' was developed under the concept that the cosmos's order and its moving rule could be directly applied to that of human body, which corresponded to the 'Theory of Hwang-No (黃老之學)'. On the contrary, Sa Sang Medicine is a thoroughly human-oriented theory formed in the Confucianism system. 2. Lee Jae-Ma's Substantialism can be briefed into 'Mind 心' (Tae Keuk 太極), 'Mind-Body 心身' (Yang Eui 兩儀) and 'Activity-Mind-Body-Matter 事心身物' (Sa Sang 四象), which respectively represents one-elemented substance, two-elemented substance and four-elemented substance. Especially, Sa Sang was used as a basic framework in which he recognized all the objects and phenomena. So, most critical significance of his substantialism consists in the intention of Sa Sang type classifying. 3. By the method of Sa Sang type classifying, Lee Jae-Ma not only redefined the main concepts of confucianism and developed a unique philosophy of his own, but also, in the field of medical science, resystemized and re-explained the structure and function of human body. 4. From the recognition that Activity-Mind-body-Matter (Sa Sang) are four different existence forms of energy 氣 (or four variation types of energy), Yi Jae-Ma thinks that the viscera of human body have a vertical structure of 'four parts 四焦' (upper, mid-upper, mid-lower and lower parts) and its physiological function is operated by the rising and falling action of four energy presentations (sorrow 哀, anger 怒, joy 喜 and pleasure 樂). 5. In "Gyuk Chi Go 格致藁", Lee Jae-Ma understood the concept of joy, anger, sorrow and pleasure on the basis of nature-emotion theory 性情論 from the philosophical viewpoint. But, from the medical viewpoint of "Dong Eui Su Se Bo Won 東醫壽世保元", he understood them on the basis of vital energy theory. That is, sorrow, anger, joy and pleasure are expression of advance or reverse of nature vital-energy 性氣 and emotion vital-energy 情氣. 6. The rising and falling action principle of four energy presentations (sorrow, anger, joy and pleasure) which produces and helps each other is an identical principles of Sa Sang Medicine, distinguished from the Oh-Haeng 五行 circulating principle in Nae Kyung Medicine. Through this principle, Lee Jae-Ma explained the viscera physiology of human body, pathology & diagnosis and pharmacology.