Abstract：The dam in Guangzhao hydropower station is the highest roller compacted concrete gravity dam in China at present. To check the mechanical indices of rock mass in dam foundation，analyze the reasonability of the survey and design information in early stage is analyzed，and the possibility to carry out optimization about the foundation plane of the 200 m dam in proper condition is considered，entrusted by the owner，Guiyang Hydropower Investigation Design and Research Institute has carried out overall and systematical geological detection and rock quantity research on foundation plane after the foundation was excavated. In this course，geological engineers have adopted ground penetrating radar(GPR)，CT(computerized tomography) of sound wave among holes，the chromatic record of boreholes，deformation modulus tests of boreholes，drilling，water pressure tests，in-situ tests and physico-mechanical properties tests in the laboratory，etc.，getting mechanical parameters information of rock mass in dam foundation. Combined with the geological information，the results are analyzed. According to the results，the rock is hard and rock mass is complete in this dam foundation；karsts are relativly not developed，and the underground water is not so active. The rock mass in dam foundation has enough compressive strength，integrity and homogeneity with enough margin of stability to resist slip and relative homogeneous deformation parameters. Except for the region along fault F1 needing special treatment，the rock mass quality in the dam foundation in the elevation of foundation plane recommended in feasibility study stage and correlative mechanical parameter index can meet the requirement of deformation of the dam foundation.
