Abstract: A seismic design study and performance verification are carried out for an out-of-code monolithic precast twin-tower structure with dual characteristics of plan and elevation irregularities and high prefabrication ratio. Based on the performance-based design method, multi-level seismic objectives of the structure are clarified, and targeted strengthening measures are formulated. In particular, performance-based design and stability analysis are conducted for cross-story columns as key components. Elastic, elasto-plastic and special analyses are adopted to systematically verify the overall seismic performance of the structure. The results show that all overall indices of the structure meet specification requirements, and the damage mechanism is reasonable and controllable. This paper optimizes and improves the traditional design ideas, and puts forward key construction structural measures to ensure the effective implementation of design assumptions, such as temporary supports for floor slabs and welded support joints of stair slabs. These measures effectively solve the connection problem between construction feasibility and design assumptions, and guarantee that the performance targets in the calculation model can be realized in actual project construction. The research results can provide feasible schemes and engineering references for performance design and engineering implementation of similar complex out-of-code prefabricated structures.