Abstract:A formula has been already developed to estimate seismic subsidence coefficient based on the area of micro-trellis pores measured by EMS and relative theories. The probability to obtain the main parameters used in the formula by measuring the area of trellis pores,reasonability and usable conditions of the formula are discussed. Furthermore,through a mathematical analysis,five stages in the development of stress and strain during seismic subsidence of loess are recognized,which gives a physical explanation for seismic subsidence of loess in terms of its microstructure,i.e,it is a final macro result accumulated by several processes of sudden changes caused by the ceaseless damage and destruction of trellis pores with different sizes.