Abstract: To address the lightweighting needs of a large unmanned aerial vehicle (UAV) fuselage, a finite element model of the UAV's load-bearing joint structure manufactured through selective laser melting was constructed in this study. Utilizing ANSYS Workbench, the joint structure's strength and stiffness were assessed under various extreme conditions and the design based on the maximum permissible stress criterion of the material was verified. On this basis, employing the variable density method of topology optimization aimed at stress minimization, this study optimizes the structure of the joint with the constraint of retaining 40% of the mass was optimized. Based on the results of the optimization, two redesign schemes were developed and validated through static analysis. The results indicate that the optimal redesign significantly achieves substantial lightweighting, reducing the mass by 13.4% compared to the original component, and exhibits the strongest load-bearing capacity among the alternatives.Under the same loading conditions, the reconstructed model of Scheme II has a smaller stress concentration than that of Scheme I. The stress concentration is reduced by 21.6% to 5.0%, 20.6% and 27.8% from work condition 1 to work condition 4, respectively. The stress concentration is reduced by 21.6%, 5.0%, 20.6% and 27.8% from Case 1 to Case 4 respectively, i.e., the aperture at the connecting plate is “fat and short”, which is conducive to the dispersion of stress, and the load-bearing capacity is stronger in the case of a small difference in weight reduction.Equally importantly, Scheme II has smaller deformation, with a minimum deformation of 0.16 mm, and compared with the reconstructed model of Scheme I, the stiffness rises significantly and the ability to resist deformation is stronger. In this paper, the combination of topology optimization and SLM can greatly shorten the manufacturing cycle and produce complex structural parts, which provides important theoretical guidance and reference for the lightweight design and manufacturing field of large-scale UAV load-bearing joint structure, advances the performance optimization and production efficiency maximization of large-scale UAV load-bearing joint structure, and promotes the innovation and development of aerospace manufacturing technology.