The persistence problem of collaborative applications is an essential issue in the research of computer-supported collaborative work. A collaborative computing environment requires a simple and transparent persistence middleware to deal with complex data accesses. Therefore, in this paper, we propose a data persistence mechanism and implement a persistence server, called Tree-Structured Persistence Server (TSPS), to support the data management for collaborative applications. The TSPS allows states of collaborative applications to be stored in a tree fashion beside tables. By introducing TSPS, the problems of collaborative applications, such as persistence data access, asynchronous collaboration, latecomer, version control, etc., can be solved easily. The TSPS was originally developed to serve as a persistence layer to support a project of computer-supported collaborative work. We intend to develop our persistence mechanism for universal use so that it can be applied in more application areas.