Abstract: Shaking table tests on the free ground consisting of saturated Nanjing fine sand are designed and accomplished. The collected acceleration signals are processed by the method of frequency-domain analysis, and the shear stress and strain of model soils are obtained using the accelerations measured at different depths. Furthermore, based on the theories of fluid mechanics, the evolution characteristics of the apparent viscosity under the action of the principal shock and aftershocks of foundation soils are obtained. The test results show that the apparent viscosity decreases with the growth of the shear strain rate under the action of the principal shock and aftershocks, and a typical shear-thinning non-Newtonian fluid feature is discovered. The apparent viscosity under the aftershocks is lower than that of the principal shock when it has the same shear strain rate. The apparent viscosity decreases as the pore pressure ratio increases under the action of the principal shock and aftershocks. The development of the apparent viscosity is affected by both the shear strain rate and the pore pressure ratio. The dual influences must be considered when the apparent viscosity is studied.