Abstract: A method of blade opening adjustment for hydraulic turbines based on substitute angle measurement is studied and presented herein to overcome the difficulty in accurate onsite measurement of blade angle and its unfavorable effect on the adjustment. We give a definition of substitute blade angle and methods for its measurement and calculation, and determine the thickness modification of adjusting shims according to a blade opening conversion ratio and the interaction between adjacent blades. This method was applied in situ to a bulb turbine and its blade openings were successfully adjusted. The results show that it improves the uniformity of blade openings and the synchronism of blade angles effectively, so as to better the hydraulic performance of turbines and their efficiency and operation stability.