Abstract: The purpose of this paper is to study the effect of the subsurface drainpipe with triangular section and pipeless wall on inhibiting water flow around the cross section in unsaturated soil. In this study, the water drainage tests are carried out by using the subsurface drainpipe with triangular section（symbol T1） in indoor soil tank, as well as the subsurface drainpipe with circular section（symbol CK） done as a control test, both kinds of drainpipes are pipeless wall. The MATLAB system is utilized to simulate the process of soil water flowing around pipe section. The experimental results show that the soil water content at the bottom of the drainpipe T1 treatment is less than that of CK treatment, and the soil salt content at the bottom of the drainpipe T1 treatment is more than that of CK treatment, indicating that the inhibitory effect of T1 treatment on soil water flow around drainpipe cross section is better than that of CK treatment. The beginning time of soil water discharging from the outlet of T1 treatment is 3.89 h earlier than that of CK treatment, and there is no significant difference between the two treatments in drainage and salt discharge（p＞0.05）. The simulation results reveal the characteristics of the drainage of this kind of subsurface drainpipe in unsaturated soil, which proves theoretically that the water content under the T1 treatment is lower than that of the CK treatment, and T1 treatment has a better inhibitory effect on the flow detour around drainpipe cross section. In unsaturated soil, the subsurface drainpipe with triangular section and pipeless wall can effectively inhibit soil water flow around the cross section than the circular section subsurface drainpipe, which is conducive to the drainage for this king of subsurface drainpipe in unsaturated soil.