The key rock mechanical problems of the underground p owerhouse in Shuibuya Project are the complicated rock structures and the contro l effect of soft rock on the surrounding rock of the grotto. In combination with the rock mechanical problems, a systematic research in different aspects of roc k mechanics based on a carefully issued research scheme has been carried out, wh ich includes the initial geo -stress distribution features, r ock mechanical properties, engineering rock classifications by different methods , numerical modeling for stability and support analysis, safety margin for over -loading and failure features, proper measures for rock excavation and supporting, etc. The results show that rock excavations of the underground powerhouse for the given geological conditions can be achieved technically . Some measures, suggested by the designer, which mainly consist of the soft rock replacements by concrete in local area below the crane beam, the shotcrete an d reinforcement by rock bolts and anchor cables in surrounding rock, resulting in a reinforced rock walls between the tailrace tubes, etc., are proved to be reasonable and effective. This paper briefly presents some relevant results.