Chang Tsai (Chang Heng-ch'ü,1020-1077) is one of the pioneers of the scholars of Confucian in the Sung, Ming dynasties. His thinking is based on the Confucian tradition, especially on the Book of Changes, the Doctrine of the Mean, the Analects and the Mencius. Differing from the position of Materialism and Idealism, the author of this paper studies Chang Tsai's theory of the "Harmony of Heaven and Man" from a position of wholism. This paper deals with three maior philosophical issues, namely, onto-cosmology, humanism, and moral philosophy, on each of which Chang Tsai has much new ideas to say with his logic of "two functions in one substance" (一體兩用). In opposition to the Buddhist doctrine of Emptiness (空) and the Taoist doctrine of Nothingness (無), Chang Tsai identifies the Vital Force (氣) with the Great Vacuity (太虛) Onto-cosmologically. In humanism, although Chang Tsai accepts the theory of Mencius that man is by nature good and the moral subjective seeks after the virtues of the human life is possible, he goes further to provide an answer to the persistent moral problem of the source of evil by defining his two key notions: the Physical Nature (氣質之性) and the Nature of Heaven (天地之性). In moral philosophy, Chang Tsai says that the great benefit of learning is to enable one to transform his physical nature himself. When moral principles and human destiny are united in harmony, they will be preserved and abide in principle. For Chang Tsai, the Way of Heaven and the Way of Man are unitied in harmony through Enlight-enment (明) and Sincerity (誠). In the conclusion, the author evaluates Chang Tsai's theory of wholism presents his profound insight in expanding the horizon of on-tology and promoting the spirit level of human life.