Abstract: Description logic is the expression of knowledge based on objects. But the existent description logic doesn't concern about the goal of organization, so it is not suited for the MAS organization model. To solve this problem, a model of MAS organization is given first, which concerns the relationship between organization and suborganization, and the goal of organization. Based on this model, a framework of description logic—ALCA is given, and the conclusion that ALCA is deterministic is proved, and the algorithm of deterministic is given. Finally, an example is given to explain the expressiveness of ALCA.