Abstract: The united front and the political consultative conference have their own historical traditions. They were gradually recognized and integrated in the preparatory process of the new political consultative conference in 1948−1949, thus making the united front obtain the organizational form of the political consultative conference, and thus the political consultative conference acquired a new basis and nature. The first plenary session of the Chinese people’s political consultative conference establishes the People’s Republic of China and has the dual attribute, both as the organization form of the united front and parties consultation institutions, and as a temporary designated authority of the National People’s Congress (NPC), this dual attribute determines the Three Files of different attributes and functions. “The Chinese People’s Political Consultative Conference (CPPCC) Organic Law” and “the Common Programme” is essentially a political agreement between the parties, and is the self-legislation of the CPPCC as a united front organization form. “The Central People’s Government Organic Law” is closer to the modern written constitution in the content, and is the political decisions of the first plenary session of the CPPCC as temporary designated authority of the NPC. Although the Three Files have different attributes and functions, they constitute the legal basis for the establishment of the People’s Republic of China and become the “unwritten constitution” of China from 1949 to 1954.