Abstract: According to the investigation data in Yellow River alluvial plain, the water content in silt roadbed is greater than the optimum value ubiquitously because of strong capillary action and water-sensitivity character, which will cause the obvious strength decay of roadbed and serious pavement damage. Through the compaction tests on silts, it can be found that the deformation characteristic is similar to the character of unbound granular in low water content and the character of clay in high water content. In order to analyze the hydrophilic characteristics of silt roadbed, the rainfall infiltration and capillary rising are simulated in laboratory tests, which reveal that the water content in silt roadbed is seriously influenced by the two factors. The speed of the capillary rising can be greater than that of the rainfall infiltration, whose rising height is over 1.5 m. To validate the above test results, filed investigation is conducted. According to the investigation, for the low roadbed with height under 2.5 m, the water contents distributing at the top and bottom of roadbed are greater than those in the middle part. For the high roadbed with height over 2.5 m, the water contents distributing at the bottom of roadbed are greater than those in other parts. Based on the resilient modulus tests on compacted silt under different water contents, the relationship between the strength and water contents is developed, showing that the resilient modulus decays rapidly with the increase of the water content. In order to provide reference for the design and maintenance of pavement structures, the resilient moduli are recommended for the low and high roadbeds separately. Based on the UU triaxial tests on compacted silt, the stress-strain relationship analysis is made on the silt under different cell pressures and water contents, indicating that the deformation modulus and cohesion force decrease seriously with the increase of the water content, and that the internal friction degree will rapidly fall down under high water contents. In one word, the silt roadbed exhibits special character with great deformation and low strength with the increase of water contents.