Video-on-Demand (VoD) systems are attractive multimedia services over the Internet. However, conventional VoD systems can not serve many viewers simultaneously because such large-scale services require considerable server load and network bandwidth. This study proposes a cooperative proxy scheme, consisting of a streaming cache and a query protocol revised from Internet Cache Protocol (ICP), to improve performance of large-scale VoD systems. The streaming cache we proposed attempts to serve the most requests with slightly computation overhead. In addition, our query protocol further extends service scalability by satisfying requests "as far as possible", although Web proxies prefer "as near as possible". Simulation results demonstrate that our proxy scheme is efficient especially in large-scale VOD systems.