With the acceleration of global economy and IT development, more and more companies are compelled to adopt a collaborative commerce paradigm to create and maintain their core competencies. To facilitate the knowledge management in collaborative work environment, this paper presents a collaborative memory model. Collaborative memory is a collection of information about knowledge usage from multi-business agents, which is domain-oriented, networked and increasing, to support knowledge management activities during collaborative work. It also serves as architecture, constructed by integrating the information about knowledge usage from multiple business agents, to support both the organization of explicit knowledge and the acquirement of tacit knowledge, which is just hidden behind the usage pattern of explicit knowledge. As the memory fragment serves as the basic unit to record and analyze the information about knowledge usage, some operations are given to concisely express complex collaborative memory analysis. Based on the above model, a web-based knowledge management system is developed for a Chinese state-owned enterprise to facilitate its knowledge management in the collaborative commerce context.