Abstract: There is an unconscious tendency in the research of Rawls’s theory, namely intuitively thinking that liberty has become a cliche topic of liberalism theory, thus considering it as a kind of consensus and will not have too much discussion. But from Rawls’s change of expression about the principle of liberty, it can be found that his thinking on liberty neither simply follows the established view of liberalism nor thinks that liberty problems have been settled without further investigation. On the contrary, Rawls’s new thinking on liberty is shown in his views of the priority of liberty and the distinction between liberty and its value. From the paper of Justice as Fairness (1958) to the book of Justice as Fairness: A Restatement (2001), which records Rawls’s understanding process of liberty principle and its connotation. Grasping the process helps us to understand Rawls’s new contribution to traditional thoughts on the connotation, extension and essence of liberty, provides a new perspective for us to better grasp the justice theory

Key words: Rawls, principle of liberty, expression, conception, extension, essence