The purpose of this study is to quantitatively measure the level of knowledge elaboration and explore the relationships between prior knowledge of a group, group performance, and knowledge elaboration in collaborative learning. Two experiments were conducted to investigate the level of knowledge elaboration. The collaborative learning objective in the first experiment concerned the understanding of curriculum objectives, and that of the second experiment was related to the theory and application of consumer behaviour in microeconomics. A total of 91 undergraduate students participated in the first experiment and 94 participated in the second experiment. Students were randomly divided into 30 groups of three or four in each experiment. Students' interactions were analysed based on the computer-assisted knowledge map analytical approach to measuring the level of knowledge elaboration. Empirical evidence from 60 groups demonstrates that the network structure entropy, degree distribution index, depth, and weighted path length of the activation spanning tree of the target knowledge map can be used for the precise measurement of knowledge elaboration. The results also reveal that knowledge elaboration is positively related to both prior knowledge of a group and group performance.