Abstract: We have developed a software tool DTST which transfers DFD into HSC according to principles of Hierarchical Structure Design method (HSD).The DTST is one of the tools in soft- ware analysis and Design Support Environment (DSE).It can be used to help user derive HSC from DFD semi-automatically in general design phase of software development,and module declaration is produced simultaneously.In addition,the user can also edit,modify,store,and manage the derived HSC interactively.