Abstract: Jinping-I-Stage Hydropower Station dam is concrete arch dam with max. height of 305 m, and it is the highest arch dam in the world. Some lamprophyre existences in foundation rock will be harmful to the dam stability and foundation stress transfer, so it has to be treated for the dam safety. It was proved that deformation modulus, compression strength, tensile strength, shear strength and Poisson ratio of lamprophyre could not meet the design requirements after high pressure cement grouting, so chemical grouting was proposed to treat the lamprophyre. High permeable epoxy resin was employed to grout the weathered lamprophyre. The physical characteristic of weathered lamprophyre has impenetrability and nonhomogeneity, however, the YDS epoxy resin possesses initial viscosity, strong affinity to mediums , excellent permeability and good ageing property. After chemical grouting, the rock mechanics characteristics are improved greatly and can meet the design requirements, it indicates that lamprophyre can be grouted by YDS epoxy resin.