Abstract: Based on the investigation on the aseismic damage of underground structures in Wenchuan earthquake, the main damage modes of underground protective arch structures were summarized. Simplified structural models for damaged arches, including two-hinged and three-hinged arches, were built according to the damage modes and distributions. Residual dynamic resistances of seismic damaged underground arches were calculated by equivalent static load method. Through case studies, moments of arches with different constraints were analyzed under shock wave load, as well as the thrust force at the foot of the arches. Then the ability of anti-dynamic load of the damaged structure after eartheuake was evaluated. It is concluded that the load capapcity of the damaged arch drops by 16 per cent or even 50 per cent when controled by bending or shear resistance, respectively.