Scale effect is one of the important aspects in the macro mechanical parameters\' research of rock mass, from a new point of view, by means of lab and field rock mechanics test, establishment of E～Vp relation, classification of engineering rock mass, numerical simulation test and back analysis based on surrounding rock\'s displacement monitoring results of Shuibuya Project\'s underground power station, rock mass deformation module\'s size effect of surrounding rock of Shuibuya Project\'s undegroud power station was studied. It\'s shown that rock mass deformation module\'s scale effect of surrounding rock of Shuibuya Project\'s undeground power station is obvious, the rock mass deformation module to tranquilization is 20% of intact rock\'s. Finally the relation between rock mass deformation modules and the scale of research was established.