The purpose of consolidation grouting for dam foundation is to improve the permeability and mechanical properties of rock masses. For permeability, the grouting effect is usually confirmed by the permeability test at check holes. But for the change of mechanical properties, it has been difficult of confirmation. Therefore, the mechanical improvement of foundation by grouting, like the changes of elasticity and strength, has not been considered in dam foundation design. In this study, in-situ experiments were made in order to examine the grouting effect on mechanical properties of rock masses.