Abstract: The main structure of this project adopts a reinforced concrete frame-shear wall system， while the cantilevered connecting part employs a two-way steel truss structure to suspend a 4-story steel frame below. The steel truss is rigidly connected to the concrete core tube of the main building. There are some irregular items in this project， such as torsional irregularity， sudden stiffness changes （coupled with dimensional discontinuities）， component interruptions， and sudden bearing capacity changes. A performance-based seismic design method was adoted. The calculations were cross-verified using multiple software programs， and a dynamic elastoplastic analysis was carried out. Detailed conceptual construction measures were proposed for structural design， such as controlling the stress ratio of key components， increasing the in-plane stiffness of the lower chord， upgrading the seismic grade of the connecting body and the components connected to it， and adopting rigid connections between the truss and the main structure. In-depth research was carried out on the vertical seismic response， stress distribution in floor slabs on both sides， human comfort， joint stresses， and construction simulation analysis of the connected structure. These efforts ensured that the structure could achieve the predefined seismic performance objectives， guaranteeing the safety and reliability of the whole building.