Abstract: A large Shuibuya hydropower plant will be constructed on the very complicated geological condition. There is a challenge appearing in design and construction of the project. Considering the results of detailed geological exploration, a quality assessment of rock mass for underground buildings of the hydropower plant is carried out. The authors describe the engineering rock mass quality for underground opening as follow: Q und-r=90+3 *R c+250 *K v-100(K 1 +K 2+K 3). The result of RMR for quality assessment of rock mass for underground building of Shuibuya hydropower plant project are illustrated. At last the progressive feedback design and informative construction related to the underground working is presented.