Abstract: In order to Study on the anti-seepage service behavior and percolation mechanism of capillary barrier cover, a full-scale cover was built in Xi'an, and rainfall and long-term monitoring tests were carried out. The results show that: (1) With the condition of luxuriant vegetation growth in summer, the water release rate with vegetation is significantly higher than that without vegetation, the former(45.8 mm) is 1.73 times of the latter(26.55 mm) . (2)With the condition of light rain~moderate rain in northwest China, preferential flow channels such as soil cracks have little influence on its anti-seepage performance, and the cause of percolation is that the actual water storage of the soil layer exceeds its theoretical water storage capacity. With the condition of heavy rain~rainstorm, preferential infiltration through soil cracks is common and frequent inducing mechanism of soil cover percolation. It will cause the water storage capacity of soil cover not to be fully developed. It is recommended to consider setting an anti-seepage margin coefficient of 1.1~1.3 .