Loess＇s microstructural parameters could be obtained well by dealing with the microstructural image.Based on the seismic subsidence experiment of loess samples taken from the Tongwei old earthquake area,we count the microstructural parameters,research the orderliness of microstructural parameters variety corresponding to different sine wave dynamic stress values and find the relation between the microstructural parameters and the dynamic stress using the soil microstructual quantitative analysis system.It appears that seismic subsidence of loess depends on its microstructure and external stress state.All microstructural parameters hold different variety in the seismic subsidence process of loess.Among them the variety of effective diameter of trellis pores,pore diameter dimension,connectivity and granule beamed degree is in conformity with the variety of residual deformation of loess.