Abstract: Democracy and liberalism can not answer for legitimacy theory according to original intent of American constitution.Republicanism is the original intent of American constitution.Republicanism pays more attention to logos of elite but not passion of mass.Republicanism is a kind of limitation on principle of liberalism democracy.There is increasing inflation tendency in democracy.Inflation of Power of Parliament and president topples down republicanism in American constitution.Excess inflation of liberalism democracy leads to republicanism revival movement.Republicanism in American constitution is worth borrowing by us in the Chinese political system reform because of its character.