Ultra-light aircraft have shown significant potential in both military and civilian applications due to their excellent weight efficiency and high maneuverability. Lightweight design is a key focus in ultra-light aircraft research, and the tensile cable network structure, with its high material utilization and lightweight advantages, is increasingly used in their design. However, the design of tensile cable network structures faces challenges related to strength and manufacturing techniques. This paper develops a nonlinear mechanical model of the tensile cable network and uses the Non-dominated Sorting Genetic Algorithm II (NSGA-II) for optimization, reducing the structure’s weight. Simulation analysis shows that applying prestress effectively reduces deformation and enhances structural stability. The results indicate that after applying prestress to some cables, the maximum deformation decreases from 6.605 mm to 1.955 mm, a reduction of 70.4%. Additionally, a novel joint design is proposed, reducing the overall structure’s weight by 15.4%. This study provides an optimized design solution for the tensile cable network structure of ultra-light aircraft and offers theoretical support for the future development of lightweight aviation structures.