Soft soil is widely distributed over the Hangzhou Region in China, so it is necessary to investigate its seismic response characteristics in anti-earthquake designs of structures. After the in situ measurements are conducted in a total of 18 wave velocity drills, the characteristics of shear wave velocity of soft soil in Hangzhou with soil depth are obtained. Its average site wave velocity is 148m/s or so. Three artificial seismic waves, with peak magnitudes of 0.98m/s², 1.96 m/s² and 3.92 m/s² respectively, act as input seismic waves. Visco-elasticity seismic response of soft soil is calculated. The average peak ground accelerations are 0.77, 0.54 and 0.43 times as those of bedrock respectively. However, the long-period response spectrum has a larger amplification. The amplification is over 1.93 when the predominant period is 1 second, varies from 0.95 to 2.53 for the 2 seconds and from 0.41 to 1.31 for the 3 seconds period.