To enable group members carry out work cooperatively, CSCW(computer supported cooperative work) systems may deal with distribution issues, solve the application-specific problems, and provide user-centered cooperation support as well. These result in the complexities of CSCW systems. However, describing the behavior of systems formally is a key step in the process of system development. In order to describe the behavior of CSCW systems clearly and make it possible to verify some specific properties of the system, this paper proposes a temporal logic based description model for CSCW systems. In this model, a CSCW system consists of running entities and information objects, and the system behavior is represented by the interactions between entities described using a temporal logic language——XYZ/E. This model can guide the analysis and design of CSCW systems.