The purpose of this article is to introduce and evaluate the John Stuart Mill's view on parliamentary politics, including the role, functions, infirmities and dangers. Being a man to believe in Utilitarianism and social reformer, Mill think that parliament was the best political institution in Britain, and the parliament had the last power to control. But at the same time, affected by the idea on majority tyranny of Alex de Tocqueville, Mill also pointed the infirmities and dangers of collective Mediocrity and class legislation. As a whole, Mill's discourse was the first and deep analysis on parliamentary politics in human history.