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