Abstract: It was found that the dynamic characteristics of loess were closely related to the microstructure.Loess formed under different circumstances conditions and stress histories has different microstructure characteristics.In many factors,the size of trellis pores,distribution in particles size and kinds of particles are key internal factors for residual strain development of loess,which also influence the stability of loess’ microstructure.Based on the microstructure images of loess samples secured from main loess regions in China such as Xi-an,Bao-Ji,,Shan-Xi,Lan-Zhou,,Tong-Wei,Yong-Deng,Hui-Ning,done by electron microscope scanning,the relevant data were obtained by the imagination processing software.The comparative analysis between seismic subsidence coefficient and those parameters show that the area of trellis pores.The declination of particle distribution and peak value of particle size distribution are well correlated to the seismic subsidence coefficient of loess.The sum of the area of trellis pores and the declination of particle distribution are defined as characteristic parameters of microstructure related to seismic subsidence of loess by authors.Then,a simple but reasonable microstructure classification of seismic subsidence is proposed in terms of microstructure,particles and pores as well as their distribution patterns and cementation.