Cicero believes that mixed constitution has the value of safeguarding people's rights and social justice, and is the best regime to maintain the political order. His thought of mixed constitution emphasizes the institutional coordination of the Senate and the People's Congress, taking account of the authority of the aristocracy and the rights of the common people, resolving interests disputes among different social levels, and coordinating public interests and individual interests. The essence of Cicero's mixed constitution is to achieve political stability. through sharing social power and establishing social relations of balanced interests. Coordination of interests, instead of restricting right with power, has become a new mode of realizing political stability. Therefore, in a highly differentiated society, the dual role of state and social mechanisms should be exerted to maintain political stability. On the one hand, government authority should guarantee the public interest; on the other hand, we should coordinate social interests through social construction.