Abstract: The coefficient of permeability of unsaturated loess is very important to seepage calculation and slope instability analysis of loess. Using the direct method to test the coefficient of permeability of unsaturated loess is time-consuming and more expensive. Now scholars prefer to obtain the unsaturated coefficient of permeability through calculation from the soil water characteristic curve (SWCC). Firstly, the saturated coefficient of permeability is obtained through the permeability tests and the SWCC by pressure plate apparatus tests. Then van Genuchten model is chosen to calculate the unsaturated coefficient of permeability by the SWCC. The results show that the coefficient of permeability of unsaturated loess becomes higher with the increase of the volumetric water content and the decrease of the matric suction. The decrease of coefficient of permeability is more 50%. In order to understand the change of unsaturated coefficient of permeability of loess, SEM tests are conducted by JSM–6701F. From the SEM of loess, it is clear that the large pores become to decrease and the small and medium pores become to increase with the time.