<p>Loess is the main material for subgrade construction in Northwest China, and water infiltration is an important influencing factor of loess subgrade disease. This work carried out infiltration tests on loess in different areas and with different compaction levels using a self-designed soil column device. In addition, the infiltration of loess subgrade was simulated using Hydrus-1D software based on the Van-Genuchten (VG) model, and compared and analyzed with the indoor test results to verify the accuracy of numerical calculations. Finally, with the help of scanning electron microscope (SEM), the reasons for the differences in loess infiltration in different regions were investigated at the microscopic level. The experimental results showed that the compaction of loess subgrade was negatively correlated with the rate of infiltration and the advance speed of the wetting front, and the Kostiakov infiltration model was more suitable for this study than the Philip infiltration model. The simulation showed that the numerical calculation results fitted well with the experimental results, and the infiltration time of water in the subgrade was positively correlated with the height of the subgrade. SEM indicated that the bonding of clay particles in loess reduced its pore area and face porosity. Among them, the sum of the area of mesopores and small pores in Xi’an loess was larger, and the surface porosity was 6.03%, which was 35.5% more than that of Lanzhou loess. The relevant research results can provide valuable references for the construction design of subgrade in loess areas.</p>