Abstract: Thousands of years ago, as a civilized community with political precocity, Chinese society formed a unique idea of the “Tianxia” (“天下”) and the theory of “the unification of the Tianxia”. After the 18^th century, with the development of natural science and the spread of the idea of “people’s sovereignty” and “democratic-republic”, the traditional “monarchical-nation” construction model with the core of Emperor, is unable to maintain the peaceful unity of the country and the stable development of society, and has withdrawn from the historical stage. After the middle of 19^th century, the Chinese people have made a difficult and tortuous exploration on how to unify China into “a real People’s Republic nation”. Ultimately, the model of “the People’s Republic nation based on socialism” which created by the Communist Party of China, not only implements and maintains the tradition of “Tianxia-China” of Chinese civilization, but also meets the basic requirements of the idea of “Democracy & Republicanism” and enriches the diversity of modern democratic republic. Thus, this special nation construction model has important theory and real sense.