Abstract: Loess is distributed widely in China and the seismic subsidence is one of the major disasters in loess areas. In this study,the subsidence deformation characteristics of loess structure under earthquake loading are organically combined with the microstructure characteristics. By electronic-microscope scanning,the microstructure and grain shape of loess are analyzed,the influence of middle-large pores on loess seismic subsidence is discussed,and the relationships among microstructure,seismic subsidence coefficient and critical dynamic stress of loess are disclosed. Key words soil mechanics,loess,seismic subsidence,microstructure,overhead pore