The security has been an important role in database systems. Authentication and access control are two major traditional policies to provide security in database system Access control policy includes two methods : discretionary access control (DAC) and mandatory access control (MAC), also known as multilevel access control. Most current database management systems (DBMSs) lack MAC. Without MAC, however, it is difficult to make sure that all users have access to only those data for which they have clearance. So it is desirable for DBMS to incorporate MAC as well as authentication and DAC. This paper proposes such a system that provides authentication, DAC and MAC also. The proposed system, called Multi-Level Secure Information Management (MLSIM), is implemented on the top of Information Management (IM), relational database management system developed by the Database Laboratory at KAIST. For implementing DAC, MLSIM provides security control commands to grant or revoke data authorization. For implementing MAC, Query modification method is used to create view by comprising security level of data object and user clearance.