Abstract: During the unsaturated rainfall infiltration process in earth and rockfill dams,the wetting deformation of rockfill materials is usually significant,which may greatly affect the overall stress-deformation characteristics of the dam. In this study,a simulated rainfall infiltration approach is used to control the wetting saturation in rockfill materials. Oedometer tests are conducted at different wetting saturation to analyze the unsaturated infiltration process and wetting deformation characteristics of rockfill materials. From the test results,it can be seen that the wetting deformation of rockfill materials mainly occurs at relatively small wetting saturation,which indicates that water in large pores does not contribute much to the wetting deformation. For the Nuozhadu slightly weathered granite rockfill material,the effective wetting saturation is less than 25.5%.