In rapidly changing large-scale information system, users? requirements are changing constantly. To address the extreme dynamism in the large-scale information system, we have proposed the Autonomous Community Information System (ACIS). It is a decentralized bilateral-hierarchy architecture that forms a community of individual end-users (community members) having the same interests and demands in somewhere, at specified time. ACIS allows the community members to mutually cooperate and share information without loading up any single node excessively. In this paper, an autonomous decentralized community communication technique is proposed to assure a flexible, scalable and multilateral communication among the community members. The main ideas behind this communication technique are: content-code communication (community service-based) for flexible information service provision/utilization and multilateral benefits communication for scalable and productive cooperation among members. All members communicate productively for the satisfaction of all the community members. The scalability of the system?s response time regardless of the number of the community members has been shown by simulation. Thus, the autonomous decentralized community communication technique reveals significant results of the response time with continuous increasing in the total number of members.