With the development of industry and the continuous improvement of people's expectations for machinery manufacturing, the role of intelligent systems in mechanical engineering is becoming more and more important. In order to improve the overall level of machinery manufacturing, it is necessary to maximize the optimization of mechanical design solutions as much as possible in mechanical design. This paper studies the application of intelligent systems in mechanical design, investigates and summarizes the application of particle swarm optimization algorithms in mechanical design and optimization, and applies particle swarm optimization algorithms to automotive machinery optimization problems, and compares the performance with other algorithms. The results show that the failure efficiency of the product has been reduced after using the optimization algorithm, and the robustness and service life have been improved. At the same time, this article also introduces in detail the specific applications of these technologies in different fields, and discusses the future development trend of intelligent systems in the field of mechanical design.