Abstract: A program OPS presented in this paper is used for searching for the optimum pathway in organic synthesis. It consists of two independent parts. The main program is a file copsi.pro, which executes the function of searching and I/O. The other is a knowledge base file dops.dat, which provides one with experimented facts about chemical reactions. Both files are written in artificial intelligent compiler language TURBO PROLOG. The program OPS can be used as an embryonic form of expert system for organic synthesis design.