The Internet enables learners to be brought together where they can cooperate in learning in groups without space and time limitations. It is, however, quite a challenge to form ideal groups in a short time and ensure satisfactory interaction for learners in cyberspace. In this study, we propose a useful grouping method to help teachers improve group-learning in e-learning by first establishing effective groups with rules based on data mining, and then facilitating student interaction using a system that monitors members' communication status. Field observations and quantitative evidence show the validity and practicability of the proposed method.