Abstract: With the increase of multimedia data in the Internet and the high-speed development of cluster, a PC-clustered high performance cluster multimedia storage system is presented, which adopts high autonomy and maintenance by itself to improve the parallelism and the expandability of the system; the CMSS adopts logic namespace management to realize a simple namespace and avoid single point of failure; it adopts data backup technology among the servers to improve the data security of the system and resolve the balance of load among the servers. In this paper the design of the CMSS is introduced in detail, and an intensive performance evaluation study on the CMSS is performed.