During thousands of years, the Chinese traditional architecture has almost followed only one pattern-the courtyard one. In this paper, the ideal living mode of "Tian ren he yi"(unity of the heaven and human beings) is expatiated. Then, the response of courtyard to this living mode is analyzed and the origin and signification of courtyard are discussed. At the end, how to keep and develop the vitality of traditional courtyard in modern times is investigated.