Abstract: In the field of political philosophy, the concept of ‘freedom’ is important and controversial. Different political philosophers have discussed and distinguished different conception of freedom, and also demonstrated their inherent logic. Starting from the social and historical conditions, Benjamin Constant compared the liberty of ancients with that of moderns. He pointed out that modern people should enjoy the liberty of moderns with no need for missing the liberty of ancients. From the inherent logic of the word ‘freedom’, Isaiah Berlin analyzed positive and negative freedom. On this basis, he presented that positive freedom logically implied the paradox and had the danger of totalitarianism, and he advocated negative freedom. Although many liberals don't agree with Berlin's argument, they believe in Berlin's claims at the bottom. However, some Republican thinkers such as Quentin Skinner did not want to abandon positive freedom, so he developed a self-consistent conception of positive freedom. But this conception with retro spirit may get little consensus in modern society. Then it needs researchers to develop a new self-consistent concept of positive freedom that can withstand the threat of totalitarianism and get more recognition. It is possible.