The main entrance building in Taiyuan Botanical Garden is a large-span cantilever steel structure with novel appearance, but the mechanical behavior of the structure is complicated. In this paper, the optimization of the components with low stress and large size in the previously designed structure was conducted, and the analysis of the optimized structure was conducted using MIDAS/Gen software. The results showed that the stress and deformation of the structure can still meet the requirement of design specifications under the most unfavorable load condition and earthquakes. Moreover, for the intersecting joint area with complex construction and large force, different reinforcement measures were proposed, and the finite element analysis of the joint was carried out using ABAQUS software to investigate the stress state of the intersecting joint area under the control condition. The results showed that stress yielding is prone to occur at the intersecting area of joint under the most unfavorable load conditions. However, appropriate stiffening measures in intersecting area can effectively improve its mechanical performance and bearing capacity, which indicates that optimization measure for this structure is feasible.