Large cavity structures are widely employed in aerospace engineering, such as thin-walled cylinders, blades and wings. Enhancing performance of aerial vehicles while reducing manufacturing costs and fuel consumption has become a focal point for contemporary researchers. Therefore, this paper aims to investigate the topology optimization of large cavity structures as a means to enhance their performance, safety, and efficiency. By using the variable density method, lightweight design is achieved without compromising structural strength. The optimization model considers both concentrated and distributed loads, and utilizes techniques like sensitivity filtering and projection to obtain a robust optimized configuration. The mechanical properties are checked by comparing the stress distribution and displacement of the unoptimized and optimized structures under the same load. The results confirm that the optimized structures exhibit improved mechanical properties, thus offering key insights for engineering lightweight, high-strength large cavity structures.