Abstract: Based on the engineering background of a large-span roof structure classified as Seismic Category I in a nuclear engineering project, this research designs an experimental model of a composite truss-concrete shear wall system exterior joint. The experiment aims to investigate the force transmission mechanism of the anchorage structure at the support joint, to reveal the crack resistance performance at the critical connection point between the roof slab and the concrete wall, and to determine the overall stiffness, load-bearing characteristics, and failure modes of the joint. A detailed finite element model of the exterior joint is developed using the general-purpose finite element software ABAQUS. The model is validated against experimental results and is subsequently used for parametric analysis to investigate the impact of stud spacing and the degree of initial imperfections in the compression diagonal member of the steel truss on the mechanical performance of the exterior joint. The research finds that the exterior joint specimen demonstrates excellent load-bearing capacity, ductility, and deformation ability. The failure process is characterized by the formation of tensile through-cracks at the slab-wall junction on the top of the concrete slab, followed by compression buckling of the diagonal web member of the steel truss near the support, crushing of the concrete at the slab bottom root, and the appearance of numerous parallel cracks in the concrete slab near the upper flange of the steel truss. The overall stress level of the steel truss and the safety reserve of the joint's load-bearing capacity are found to be high. The design of the studs is deemed reliable, and the spacing of the studs can be appropriately increased within the allowable limits. The initial imperfection of steel truss have no significant effect on the mechanical performance of joint. After reaching the peak bearing capacity, large initial imperfection of steel plate will significantly reduce the bearing capacity of the joint.