The expansive soil is studied as the object of the research in Yichang City, Hubei Province. Different content of lime, cement, coal fly ash and weathered sand are put into the expansive soil to modify it, then the unconfined compressive strength is tested under standard conditions with the days of 7, 14, 28 d. The research shows that the unconfined compressive strength can be improved in an effective way with the above four materials, the strength of expansive soil with cement grows obviously in the first 14 days, then the growth rate slows down with the curing age goes up; the unconfined compressive strength of expansive soil with lime is nearly in a linear growth trend with the curing age goes up; the unconfined compressive strength of expansive soil with coal fly ash is also in a linear growth trend, but the unconfined compressive strength is smaller than that of expansive soil with lime; the curing age has little effect on the unconfined compressive strength of expansive soil with weathered sand.