This research aims to develop an expert system for the optimal stiffness design of composite laminates. The optimal stiffness design of composite laminates was performed under the constraint that the strain of a composite laminate does not exceed a required strain and design heuristics. For optimal stiffness design, the optimal design of stacking sequence was performed by enumeration method, expert system shell CLIPS and classical laminate theory. The optimum stacking sequence combination was obtained by using the discrete ply angles such as 0°,±45°and 90° and the design heuristics for stacking sequence design. In this expert system, the design heuristics were stored in the knowledge base of the CLIPS. The present results showed good agreements with the previous studies. The total number of plies in the optimized laminate could be reduced when to be compared with the non-optimized laminates.