Abstract: Multiple spectrum analysis method and single spectrum analysis method are two stand analysis methods which are used for the pipe seismic analysis in nuclear power plants.Multi-support excitation is applied to pipe supports in multiple spectrum analysis method,and uniform excitation is applied to pipe supports in the single spectrum analysis method.Variation of seismic motion according to space position is considered in the multiple spectrum analysis method.In this paper,multiple spectrum analysis method and single spectrum analysis method are used in the seismic analysis of VVP line after damper-cutting,to compare the effect on damper under these two analysis methods.The results reveals that,the conservatism of two analysis methods is different,and for the auxiliary pipes coupling with primary pipes,multiple spectrum analysis method can be applied in the seismic analysis;On the other hand,for the small scale pipes decoupling with primary pipe,single spectrum analysis method is conservative in the seismic analysis.