To solve the problem of impervious material locally used in hydraulic-power engineering in a highquality way, experimental research was carried out to verify the feasibility of impervious material of fully weathered basalt used in Shashubao Reservoir. In accordance with distribution characteristics and properties of fully weathered basalt, experimental research mainly included physical and mechanical properties and osmosis properties. Research shows that earth material of fully weathered basalt is high liquid limit gravel silty clay without expansibility, whose content of organic matter and water soluble salt meets the quality requirements of impervious material in core dam engineering. It can be used as impervious material for fully weathered basalt has good compressibility of low maximum dry density, and high optimum moisture content.