In recent years, seismic safety evaluation has been conducted at many engineering sites in the Tianjin area where dynamic nonlinear soil parameters can be obtained. In this study, we collected 83 seismic safety evaluation reports in this area and obtained 1 650 groups of dynamic triaxial data on soil from 202 boreholes. We then determined the representative values and their standard deviations of different types of soil at different intervals and different depths. A typical site Ⅲ is taken as an example. By using the equivalent linearization method to calculate the seismic response of the site under different ground motion intensities and phases, we studied in detail the influence of variability in the dynamic shear modulus ratio and damping ratio of the overlying soil on the peak ground acceleration and response spectrum of the site. The results show that the peak ground acceleration and ground response spectrum of the site increase or decrease with an increase or decrease, respectively, in the soil dynamic shear modulus ratio. However, the acceleration and spectrum increase or decrease with a decrease or increase, respectively, in the soil dynamic damping ratio. Under the input of a great earthquake, the soil dynamic shear modulus ratio decreases, and the peak ground acceleration and medium and high frequency portions of ground response spectrum decrease clearly. The change in the dynamic damping ratio also has a certain impact on peak ground acceleration and the ground response spectrum, but this is not as obvious as the change in the soil dynamic shear modulus ratio. Under the input of moderate and small earthquakes, variability in the soil dynamic shear modulus ratio and damping ratio have little impact on the peak ground motion acceleration and ground response spectrum.