How to meet the settlement requirements both within construction process and post-construction and to improve impermeability of embankment is a key technology in building the passenger dedicated line in collapsible loess area. On the basis of the subgrade structure with lateral-constraint and seepage control, the effects of lateral-constraint and seepage structure in high speed railway subgrade on improving the seepage property of foundation soil in collapsible loess area are researched. Lime-soil compaction pile and cement-soil compaction pile with different pile spacing are adopted as lateral seepage control structure for indoor model test. According to different fillings of compaction piles and pile spacing, the change of moisture content of the foundation soil in different position and depth is measured. It is concluded by comparative analysis that setting compaction piles has a significant effect on the lateral seepage control compared with natural foundation. And with the spacing decreasing, the change of moisture content of the foundation soil decreases gradually, which means the slower the flowing speed, the better seepage control effect. In terms of the two kinds of compaction piles mentioned above, cement-soil compaction pile has a better effect on seepage control than lime-soil compaction pile. The research results can provide a reference for similar projects.