There is mainly granite in the dam site area of Nuozadu waterpower station. The study and know of the engineering geology feature of granite body, rational selection of the mechanics parameter of rock body are very important for the safty and save in dam construction. According to a lot of geological exploration and testing study, we have achieved the scientific assessment of genesis, distribution and quality of granite body in dam site area, proposed the suggestion of rational and reliable parameter indices, which can provide the reliable geological basis for the construction of hydropower station.