In this study, a knowledge-based expert system for the optimal design of composite structures subjected to various loading conditions and rules of design heuristics was developed. The optimal stacking sequences and total number of plies were obtained by integration of a knowledge-based expert system, optimization programs (enumeration method and genetic algorithm) and composite analysis programs. The optimal stacking sequence combinations were drawn from discrete ply angles and rules of design heuristics stored in the knowledge-base for the given application of interest. For the design of the tapered composite laminates, a patchwise layup design method was developed. In this approach, the weight of composite laminates with ply drop under strength constraint was minimized and for this purpose, stacking sequences and the number of plies were optimized. The design variables were the discrete ply angles such as 0˚, ±45˚, and 90˚ and the number of plies in each patch. For the easy manufacturing and the assessment of manufacturing complexity, manufacturing cost was introduced. The composite laminates designed by patchwise layup design method were compared with the uniform thickness laminates. It showed that the optimized layup could considerably reduce total weight of the composite laminates.