In this paper we present a database design tool set (DBTOOLS) which consists of three tools: Extended E-R model design tool(EERD) ,E-R model to relational model transformation tool (ERTR), and DFD,DD to relational model transformation tool (DDTR). DBTOOLS works in a combined mode of automatic transformation and human interference, and supports conceptual structure design and logical structure design of relational databases. In the design of DBTOOLS,we emphasize its support to semantic information description and utilization,and incrematal development of database application systems.