Using the methods such as infiltrating water experiment, total porosity, measurement of susceptibility and magnetic susceptibility, the authors did some research on the permeability of S1-L4 layers in the Changwu loess section and on its mechanism of formation. The research result shows that the infiltration rate of the loess and red-brown paleosol layers changed greatly. The results showed that conditions and laws of enrichment of the loess groundwater were controlled by climate changes during Quaternary. This has an important application value to development and utilization of loess water resources.