Abstract: In order to study the influence of groundwater on the modified basalt residual soil, the soil-water characteristic curves of two different proportions soils treated with lime, fly ash and cement and the untreated soils(control group) were tested, and the experimental data were fitted.The results showed that:(1) The soil-water characteristic curve consisted of the descending section and the flat section.The matric suction in the descending section had a great influence on the properties of the unsaturated soil, but the matric suction in flat section had small influence.(2) The volumetric water content decreased gradually with the increase of matrix suction, and the saturation degree and matrix suction of modified basalt residual soil showed similar characteristics, which showed that the modified basalt soils had good water holding capacity.(3) The VG model, Brooks-Corey model and Fredlund-Xing model were in consistent with experimental results.Especially, these models had good fitting effect for modified soil 2,and had relatively worse fitting effect for modified soil 1.In consideration of water stability, modified soil 2 should be selected.