Thin-walled cylinder welding method and thin-walled cylinder welding tool

The invention provides a thin-walled cylinder welding method. The thin-walled cylinder welding method comprises the following steps that S1, a main welding seam of a thin-walled cylinder is welded; S2, the thin-walled cylinder is hoisted to the welding position; S3, the welding position of a reinforcing ring is determined; S4, a multi-function disc supporting frame is installed in the thin-walled cylinder, and the roundness of the thin-walled cylinder is adjusted to meet the requirement; S5, the reinforcing ring and the thin-walled cylinder are sleeved, and a welding platform of a movable suspension bridge welding frame is moved to the reinforcing ring; S6, a welding worker sits on the welding platform for welding; S7, the thin-walled cylinder is rotated till a non-welding area is located at the side of the welding platform; S8, the steps S6-S7 are repeated until one circle of the reinforcing ring is totally welded to the thin-walled cylinder; S9, the welding platform moves to the next reinforcing ring weldin