Abstract: The 3 D seismic response analysis of underground group caverns for underground plants of large hydropower station or nuclear power station or subway station is difficult because of its dynamic interaction with the surrounding rocks. The dynamic characteristics of surrounding rocks are not only concerned with their constraint on underground structure, but also related to the earthquake input in the dynamic interaction analysis. In this paper, the dynamic impedance is studied using so called damping solvent extraction method,and a practical approach with better accuracy and lower computational cost is proposed for large underground caverns in rock.Then the anti seismic safety of Xi luo du large scale underground caves is evaluated and possible seismic countermeasures are suggested.