Abstract: The embedded database system is generally used in the equipments provided with self-control ability and always deals with real time transaction. It is particularly urgent to establish embedded Real Time Database System (RTDBS) with the technique of Main Memory Database (MMDB). In this study, the design strategy of an embedded main memory database SQLmmdb is presented. We propose an improved index structure on the base of T* tree (called T** tree) and design a non-log recovery method which is fit for MMDB. And we also compared SQLmmdb on performance with the embedded DBMS SQLite which is now widely used in many applications. The experiments show that the speed of SQLmmdb is accelerated a lot, at the same time the space occupied by the database files reduced remarkably. SQLmmdb is a high performance main memory DBMS model which is suitable for embedded system.