The reasonable selection and modification of ground motion records is an important factor for the reliable nonlinear time history analysis results of structures. 7 groups of ground motion records were selected and modified by spectral matching and spectral acceleration corresponding to the fundamental period of the structure Sa(T1). Then, a 5-story and an 11-story planar reinforced concrete frames were analyzed via nonlinear time history analysis method with a single intensity measure under the spectrum-matched and modified ground motion records respectively. Maximum inter-story drift ratios and maximum residual inter-story drift ratios of the structures were taken as engineering demand parameters (EDPs) and the dispersion and bias of EDPs were also discussed. The analysis results show that choosing reasonable ground motion records to be modified and matched with the target spectrum can reduce the dispersion of the structural response results without conspicuous bias. With the same intensity measure Sa(T1), the analytical response results of the structures will decrease with the increasing of spectral shape parameter ε of the condition spectrum.