Learner autonomy has become a hot topic and goal in the research of foreign language education. However, it is the most difficult question to define language learner autonomy and any answer to it is likely to be subjective. On the basis of expounding upon the different definitions concerning the research on learner autonomy in language teaching and learning, this study was to explore how cooperative group learning helps to improve learner autonomy. The survey's findings indicate that the group work helps to improve students' learning attitude, interest and motivation. It also reveals that students' language competence and awareness of using learning resources are improved. This article discusses plausible explanations for the survey findings and makes recommendations on the roles and knowledge that language teachers should play and have to facilitate the development of learner autonomy.