The process of mould design depends on one's engineering knowledge and design experience. Knowledge-based engineering (KBE) adequately utilizes such knowledge and experience to design. KBE is a very important approach for increasing the intelligence and speed-up of the time of engineering design. In recent years, the use of genetic algorithms, as an optimization method, enables a rapid development. It searches the optimum solution for a problem using the principle of "survival of the fittest". In the process of mould design, constraint conditions for important parameters are set up. Then, a genetic algorithm is used to code these parameters and search for the optimum (or approximate optimum) solution of these parameters. Compared with general KBE, the KBE based on a genetic algorithm enhances the efficiency of design and the precision of solution. It not only makes use of the knowledge and experience of experts and designers, but also utilizes the great ability and generality of genetic algorithms in searching for an optimum solution.