Considering the importance of user-innovation knowledge to product and service innovation, this paper proposed knowledge discovering and analyzing methods on user-innovation communities based on weighted knowledge network (WKN). First, web mining methods were used for getting forum posts in virtual user-innovation communities, then the acquired keywords and the statistical data were processed and integrated into a WKN model. Next, based on the WKN model, the paper proposed new methods to discover the core innovation knowledge, the developing innovation knowledge and the potential innovation knowledge through analyzing the structure of WKN model, including weights of nodes and edges, cliques, the strong or weak ties, etc. Finally, Xiaomi community was taken as the study case to verify the validity of the methods. Compared with the existing method of user knowledge discovery, the presented methods are more quantitatively, conveniently and visually and provide new tools to study and utilize the user-innovation knowledge in enterprise virtual communities.