This paper puts forward a novel approach called cement-modified soil (CMS) blocking cushion technology to reinforce the subgrade in saline soil region: the cushion layer of composite foundation and a roadbed partition layer are combined into one CMS layer. The effectiveness of the proposed approach was verified through outdoor experiments on the saline soil section (DK821+600-DK821+900) of the newly built Lanxin High-Speed Railway. The experimental results show that the CMS layer can effectively adjusts the pile-soil stress ratio of the composite foundation, thereby enhancing the bearing capacity of the composite foundation and reducing the total settlement of the subgrade; it is also verified that the CMS layer greatly suppresses the upward migration of capillary water and water vapor in the foundation soil, and curbs the migration of salt, preventing the secondary salinization of the railway subgrade. Overall, this research provides a simple and low-cost subgrade reinforcement technique for saline soil regions, shedding new light on the engineering application of the CMS.