Abstract: In the experimnt,two kindes of machined Y-rings and one pulled Y-ring were applied to Canopy welds of the control rod drive mechanism of nuclear power plant,and the effects of different Y-rings on the welding process and weld properties of Canopy welds were studied.The results show that the machined Y-ring is a whole ring,which is more advantageous to spot welding than drawing Y-ring.The machined Y-ring(tolerance control)is similar to the drawn Y-ring assembly clearance range,which is larger than the machined Y-ring assembly clearance range,which is more conducive to engineering application;The structure of the Canopy welds formed by the three Y-ring melting is mainly composed of ferrite and columnar-austenite,and there is no obvious difference.After 23.1MPa to 23.3MPa water pressure test,there was no leakage or deformation on the surface of the three Y-ring Canopy welds.This study provides valuable experience for the application of machined Y-rings to Canopy welds of control rod drive mechanisms in nuclear power plants.