Abstract: As one of the most important contemporary thinkers of the West,the second-generation leader of Frankfurt School in Germany,Habermas is the most important representative of the critical theory and neo-Marxist.Habermas'sphilosophy of language is rigidly different in the different stages.Comparative analysis between early stage and late stage makes it important for us to understand Habermas' mature philosophy of language.It starts from the following six aspects:validity claims,speech act theory,the model of language use,ontology,life world theory,ideal speech situation.