Abstract: In this paper, scanning electron microscope is used to observe the microstructure of the artificially prepared structured collapsible loess samples under different generalized stress state. A quantitative analysis technique, named SQM is used to analyze distribution of pores and their orientation of two pairs of sample before or after inundation respectively. It is shown that the high vertical stress can only compress macropores to make them smaller. If the sample is inundated under high vertical stress, all pores will become smaller. As for the sample inundated under low vertical stress, microcracks emerge near some macropores while other pores become smaller. However, the difference in orientation of particles of two samples under different generalized stress state is not so apparent as that in pore distribution except for the sample inundated under low vertical stress.