Abstract: In this paper,a PROLOG system based on a relational data base is described. The direction of my work is to produce a PROLOG system that is equally good for both data base and programming purpose. The method of our design is to combine the existing relational data base with PROLOG system in such a way as to allow deduction and control to be performed by PROLOG excuting mechanism while large amount of data retrieval to be handled by a relational data base. This system is implemented on IBM-PC in C programming language.