This paper designs and implements CSMSSim, which is a hierarchical simulation system for Clustered streaming media server (CSMS). CSMSSim is e±cient and accurate, because it is based on an accurate and simpli¯ed simulation model of CSMS, and the nec- essary hardware resources' parameters in CSMSSim are obtained through the stress testing based on a practical CSMS testbed with 6 nodes. In addition, CSMSSim is highly con¯gurable, because it has a hierarchical architec- ture with independent algorithm layer, logical layer and hardware layer. Therefore CSMSSim can adapt to various streaming media applications, and the rapid increasing of the streaming media service systems' scale in nowadays and the future. Finally, the simulation experiments on the CSMS algorithm evaluation based on CSMSSim show the powerful function of CSMSSim, and give guidance about improving the performance of CSMS by choosing appro- priate memory cache replacement algorithms and disk data allocation algorithms.