Research conclusions: It is feasible to use lime as ameliorant of expansive soil. The component of granule, physical and mechanical properties and the swell-shrink characteristics of expansive soil with lime are obviously ameliorated, the mechanical strength and water stabilization are improved, and the requirement of the backfill of the railway subgrade can be met. The ratio of the lime is 6% in the medium-grade expansive soil and 5% in the weak-grade expansive soil. The higher-grade lime over third-grade should be used and more lime should be used when using low-grade lime.