Abstract: The expansive soil is a final man-made shield——basement material of cushion in underground site to treat waste with heavy radioactive. How its mechanical properties under high compaction is the vital to the long term safety of underground handling site. The results of uniaxial and triaxial tests for high compaction expansive soil with the different moisture content show that it has the no-recoverable plastic deformation, and the fixed mechanical strength and the good ductility.