Peer-to-Peer (P2P) system has become one of the hottest research topics, its excellent characteristics of fully decentralized control and self-organizing make it attractive for some particular applications. However, it faces more technical problems than client/server architecture.In this paper, we propose SBARC, a new P2P file sharing system which takes into account the tremendous resource differences among peers to improve system performance. SBARC divides the peers into supernodes and ordinary nodes and most workloads are taken on supernodes. The main contributions of SBARC are (1). A supernode based routing algorithm which can reduce the average routing latency; (2) Routing information are cached to further reduce the routing cost; (3). A coordinate file caching scheme which achieves efficient utilization of free storage space. Our simulation results show SBARC routing and caching schemes can achieve better performance than previous approaches.