The invention relates to the technical field of welding, particularly to a device and a process for backstep welding of a damping spring disk. The device comprises a rotary table, a locating plate, a vertical plate, a rotating cylinder, a liquid storage cylinder pressing plate, a spring disk locating pin long seat locating plate, a spring disk locating pin long seat, a spring disk locating pin, a spring disk pressing plate, a spring disk locating round pin, a spring disk locating long pin, a spring disk locating pin seat, a liquid storage cylinder locating plate, and a reinforcement plate. Compared with the prior art, the disk is three-point located by the aid of a tooling and fixedly clamped through the rotating cylinder, welding thermal deformation after welding is reduced, dimensions after the welding are stable and reliable, and adjustment is convenient. The structure of the device for the backstep welding of the spring disk is simple and stable, the maintenance cost is low, and the device is convenient to maintain.