Aiming at the drawbacks that are found by analyzing online teaching at the present, we discuss the impact of concept and technology of Web2.0 on collaborative learning and knowledge construction. In order to improve the quality of online teaching and learning, a new collaborative learning mode is proposed based on constructivism theory and Web2.0 technology in this paper, and its characteristics is interpreted in detail. The mode includes some popular technologies, such as blog, wiki, tagging, and so on. With the further popularization of Internet and mobile Internet, the new mode will have an important and positive impact on online teaching, which is beneficial to learners by providing hierarchical online teaching resources, and training autonomous learning ability of learners in the long run.