Abstract: Cooperation in virtual enterprises is hierarchical, dynamic and self organizational A hierarchical cooperative model （HCM） is proposed to describe the whole cooperative relation and the cooperative way in virtual enterprises based on these three most important characteristics A four tuple is used to formally describe cooperative actors in virtual enterprises Then, a mixed strategy is discussed to implement cooperation at collaborative level, which is the second logic level of HCM HCM can not only describe and predict the whole cooperation status in virtual enterprises but also provide support for system decision making