Taking a thick silt site in Binhai District of Tianjin as an example, the equivalent linearization method (LSSRLI-1) and the analysis method of soil earthquake response (SOILQUAKE) were used to calculate the earthquake response of soil layers under seismic ground motions of different fortified levels. The results showed that:(1) Compared with the results of the new zonation map, the equivalent linearization method may underestimate the seismic action of the thick silt soft site, or even underestimate the fortification intensity of the site; (2) The method of software SOILQUAKE can still show a certain amplification effect in determining the design seismic parameters of soft site, especially under strong earthquakes, it overcomes the phenomenon that the design spectrum is obviously low and wide in the calculation of soft site, which can provide a reference for the determination of fortification parameters of major projects in soft site; (3) The design ground motion parameters of soft site determined by the method of software SOILQUAKE are greatly superior to the results of the new zonation map. Considering the coordination with relevant seismic fortification codes, a large number of strong earthquake records need to be further input, calculated and verified for other types of soft sites, so as to be better applied to actual projects.