Public reason,the core of modern Western political philosophy and public philosophy,is the basis of the legitimacy of public life.Scientific development rationality is the prominent feature of public reason in the transitional society of contemporary China,which is based on the following two reasons: one the best response and solution to the problems existing in the transitional society of China;the other sublation and innovation of public reason in Chinese and western history.The public reason of sscientific development rationality lies its feature in the core values of socialism with Chinese characteristics.