With the changes of learning psychology and information technology, CSCL tools should also keep up with the times and meet the growing needs of learners. The appearance of RIA can make up the deficiencies of Web-based CSCL tools at present. With the use of RIA, the next generation tools could be realized with high interactivity and richer user interfaces. Silverlight is one of mainstream technologies of RIA, and it has the advantages of better user interfaces, high development efficiency, newer way of communication, and so on, which other RIA technologies could not reach. In order to facilitate collaborative knowledge construction of learners, the paper design and develop a Web-based CSCL tool which has the function of real-time interactivity with words or graphics.