Abstract: Dynamic description logic is proposed for formalizing multi-agent cooperation process with a clearly defined syntax and semantics. By combining the features of knowledge representation and reasoning of description logic and action theory for multi-agent interaction, the present logic is effective and significant for both static and dynamic environment. On the static side, a description logic is employed for the representation and reasoning of belief and goal. On the dynamic side, an object-oriented method is adopted to describe actions. The description of each action is composed of the models, preconditions and effects, which reflects the real changes of the world and is very suitable for belief revision and multi-agent planning. Based on the logic, how to form joint goal for multi-agent cooperation is investigated. In particular, an effective dynamic planning algorithm is proposed for scheduling sub goals, which is greatly crucial for coordinating multi-agent behaviors.