Abstract: In order to prevent secondary salinization of subgrade caused by the upward migration of salt with capillary water,a self-designed indoor test device for simulating water salt migration in subgrade was used to compare and analyze the blocking effect of partition layer at different locations on capillary water and salt migration,targeting two types of subgrade fillers,low liquid limit clay and gravel soil,which are widely distributed in inland saline soil region.The time effect of capillary water and salt migration was revealed.Research results show that in inland saline soil region with sufficient groundwater supply,whether using low liquid limit clay or well graded gravel as subgrade filling,if the partition layer is set at the lower part of the roadbed,the capillary water can rise through the subgrade to a stable position of 10~15cm inside the partition layer,and the salt content increase is small,which indicates that the gravel partition layer can effectively prevent the rise of capillary water,avoid secondary salinization of the subgrade,and meet the partition requirements of low subgrade construction; Comparing the two working conditions of the partition layer set at the bottom of the subgrade and the lower part of the roadbed,it is found that the rise height of the capillary water in the partition layer is about 15~20cm in the former condition,and the rise height of the capillary water in the separation layer is about 10~15cm in the latter condition,indicating that setting the partition layer at the lower part of the roadbed is safer for its roadbed and pavement structure; Since the separation layer located at the bottom of the subgrade is easily affected by surface runoff or rainfall water immersion,the partition layer should be set above the historical highest flood level,and the safety height should not be less than 50cm; In addition,compared with gravel soil subgrade,capillary water migrates at a higher height inside clay subgrade and requires a longer time for stable migration.