The invention belongs to the technical field of bridge construction, and particularly relates to a system for improving the anti-seismic performance of spandrel structures of large-span deck type archbridges, which comprises at least two stay cables, the stay cables are arranged in axial symmetry along target pillars, one end of each stay cable is connected to the top of the target pillar, the other end is connected to a stabilizing member with high rigidity, and the stay cables are in a tensioned state. The target pillars of the system disclosed by the application are determined in the process of design; for spandrel pillars requiring the enhancement of anti-seismic performance, the target pillars are stayed by the stay cables, thus the target pillar is changed from a cantilever structure into a structure with elastic supports arranged on the top, the root bending moment and pier top displacement of the target pillars are remarkably reduce when the target pillars receive seismic force, consequently, the injuries of the target pillars can be remarkably reduced, the destruction of the spandrel pillars can be effectively reduced, the collapse destruction of the spandrel pillars is prevented, and the anti-seismic design of such bridges is more reasonable.