Abstract: With the development of the Internet, the scene of storing multimedia files is increasing and cloud storage system has become the focus of the Internet field. Many cloud storage systems provide applications with data storage, query and computing service. A lot of applications have a large number of small-sized and duplicate multimedia files. Traditional distributed file systems are not suitable for storing and accessing multimedia files. Because in these systems, multimedia files are usually divided into several blocks which are stored on many data servers. Every time when applications need to get the file content, these file systems need reconstructing. This strategy can cause the problem of consuming more resources when users access the multimedia files. In order to let these applications with high data redundancy store multimedia files efficiently at a low cost, we propose a model of distributed directory tree to describe the logic structure of directories in the data center. Afterward, we design and implement a distributed multimedia file system named MFCSS which can support data deduplication and the logical expansion for directories. The experiment results show that the system not only has good performance when it saves multimedia files with higher redundancy but also can effectively improve the efficiency of disk storage. Moreover, the MFCSS system has good scalability and can simplify the process of managing multimedia files stored in distributed storage environment for applications.