Abstract: The rotor support of Wudongde Left Bank Hydropower Station adopted weak-constraint symmetrical welding process, which breaked the tradition of rotor support-bound welding process in the history of hydropower, and its main feature was that welding and cutting of horse riding boards were cancelled. The welding process could shorten welding period, reduce internal stress of weld, and improve welding quality of rotor bracket. The control method of weak constraint symmetrical welding process of disc rotor support in the Wudongde Left Bank Hydropower Station was summarized in the paper, and the trend of changes in the characteristics of rotor support during welding and process measures of welding quality control were analyzed, which provided scientific basis for the control of weak constraint symmetrical welding process of large disc rotor support in the future.