The causes and status of saline soil in southern Xinjiang are stated simply, and the properties of it are presented based on experiment. Much emphasis is laid on the improvement mechanism design and the scheme comparison. On this foundation, a series of tests are conducted. The functions of different subgrade fillers and the reasonable proportion of them are studied. The result reveals that improvement scheme II-3 can effectively decrease anion content in saline soil, and mixed with cement and active material fly ash, can significantly increase the strength of the soil mass, and decrease water involved in expansion and frost heave. The research findings can provide an economical and applicable reference to the solving of problems such as frost heave, salt expansion and melt sinking of the saline soil subgrade.