Abstract: In this paper the microstructure of seasonal frozen soil of the road between Changchun City and Jilin City is studied with the technique of SEM. Quantitative analysis which is about the granularity composition, the characteristic of structure units and pores is carried out, also the relationship between moisture content translocation and microstructure is discussed. It is shows that in the microscopic level the microscopic particles and structure unit have the following features, such as the directionality is not obviously, much more pores is developed in it, and even in the condition of clay content higher, the pore aperture is mainly distributed in the 1-2μm, i.e. the capillary pore is abundant. The resultant shows that the characteristics of soil sample is isotropy, namely the moisture content translocation behavior is same both in horizontal and vertical direction under the same external conditions.