Due to the large size and heavy mass of ultra large bearings,the bearing adjustment is not flexible,meanwhile,the positioning is not accurate during the drilling process.In response to the above situation,a rotatable support device for drilling has been designed.This device provides a workbench that can complete rotation and support based on the characteristics of ultra large bearing rings,effectively solving the problems of chamfering and tapping machining of installation holes for large megawatt bearing rings,and improving work efficiency.