Abstract: Different damping ratio values must induce different outcomes of structural responses. In this paper, 434 horizontal seismic records are selected from PEER strong ground motion record database, and are divided according to the soil conditions (SC) and the design characteristic periods (DCP) in the Chinese current seismic design code. The elastic-plastic time-history analysis is carried out for a single degree-freedom structural system when the damping ratio values are 0.02,0.04,0.06,0.08, 0.10 respectively. The damping ratio influence factor curves are obtained under different damping ratios, different SC and different DCP. The results show that the change of damping ratio influence factors is not remarkable along with the change of yield strength coefficient, it could be ignored in design; an approximate linear relationship is showed between the damping ratio influence factor and natural periods of the structure , damping ratio influence factor values changes between 0.75―1.30; the insensitive regions of damping ratio influence factor are existence, and its distribution is influenced by the SC and DCP. Finally, by a non-linear regression analysis, the expressions of the damping ratio influence factors are presented under different SC and DCP.