This paper describes a concept of social robot systems as a self-organizing system. A distributed autonomous robot system is not autonomous as a group if the system totally depends on external intervention to maintain its fundamental functions. We discuss the meaning of autonomy for group robot systems and a concept of collective autonomy as a fundamental framework for design ofthe social robotic system. We first discuss the difference between cooperative and self - organizing behavior. After a brief review of classical self-organizing system theory, we present the self-referential coupling of self-organizing systems as a design framework ofthe collective autonomous system. Through a primitive simulation model, we also discuss the relation between redundancy and optimality in the system structure.