This paper studies the application of ANSYS in the optimization and lightweight of mechanical structures. It introduces that ANSYS software can simulate a variety of physical phenomena and the functions of each analysis module, and elaborates on the importance of the optimization and lightweight of mechanical structures. It also explains in detail the application process in structural optimization and the lightweight analysis methods such as topological optimization and material replacement. The conclusion points out that ANSYS plays a crucial role and is constantly developing. In practical applications, its advantages should be fully exploited to promote the progress and sustainable development of the industry.