Abstract: In order to study the water vertical infiltration and the unsaturated hydraulic conductivity function of the compacted loess, two groups of infiltration tests are conducted on the unsaturated compacted loess columns in the laboratory. In the constant-water head infiltration tests, both the cumulative infiltration and the wetting front distance are in a good power function relationship with time. A linear correlation exists between the cumulative infiltration and the wetting front distance. The infiltration rate, which is inversely proportional to the wetting front distance, decreases rapidly with time after the initial infiltration and finally reaches a steady seepage. In the rainfall infiltration tests, the van Genuchten and Fredlund-Xing equations are used to model the soil-water characteristic curve (SWCC) for each soil. Both the models capture the curve reasonably well over the entire range of the measured suction. The unsaturated hydraulic conductivity calculated using the instantaneous profile method has an exponential relation to the volumetric water content. Meanwhile, the van Genuchten and the Fredlund statistical modeling formalism are used to predict the hydraulic conductivity function, respectively. By comparison, the predicted values of the van Genuchten hydraulic conductivity model are much closer to the experimental values.