Abstract: The capillary water can reduce the strength of the silty subgrade and affect the durability and usability of the pavement. The key of treating silty subgrade is to reduce and control the action of the capillary water. Three methods, solidification method, geotextile speration method and butter layer method, are applied for treating the silty subgrade by means of the capillary model test and the field test. The model test results reveal that the effect of the lime-soil cured for 45 days adding composite geomembrane is similar to that of the gravel cushion and coarse sand cushion. The field test results indicate that the effect of the gravel cushion and the coarse sand cushion isolating capillary water is better than that of the composite geomembrane and the 3% cement-soil cushion; and that of the 5% lime-soil is the worst. Based on the two test results and practical engineering, the method of lime-soil adding composite geomembrane is recommended to treat the capillary water in silty subgrade.These two tests results can be the basis of the engineering design.