Abstract: Aiming at the requirement of flexible cooperation mode in open environment,and the “ill-structured” and “creativity-needed” characteristics of cooperative design problem,this paper presents an RPACTI Agent model．This model extends traditional modes that only have determinate cooperation interfaces,by adding indeterminate interface description and invoking methods．It is proposed a new mode based on three kinds of interfaces：capability,potentiality and interest． Furthermore,the model supports a hybrid mode of determinate,tentative and weakly-constrained collaboration,enabling agents to cope with dynamic and uncertain problems in a more flexible manner． Policy-based management is also integrated into the model, ensuring that the self-organizing collaboration is demand-oriented and controllable．The model is competent for solving the cooperative design problems in open environment because of its success rate,efficiency and flexibility．