The invention discloses a method of repairing and assembling vaporization gas hood of converter vaporization cooling boiler, including steps: 1, a direct pipe on one terminal of a small three-way pipeis welded with a circular header without preset assembly balance according to design or technical needs of drawing; 2, the circular header is disposed on ground horizontally, axis of the small three-way pipe is in a vertical direction with a direct pipe on one terminal of the small three-way pipe welded with the circular header; 3, two forked pipes on another terminal of the small three-way pipeare welded with discharging pipes respectively. In the repair and assembly method provided by the invention, the small three-way pipe is assembled without preset assembly balance, waste of materials is reduced, materials and energy are saved; the header is disposed on the ground horizontally, then the assembly size can be controlled better, and provides a beatiful assembled shape, without restriction of operation space and eliminates safety accidents exist in air operation; welder can weld in positions of overall planes which can reduce low efficiency of each worker and ensure weld quality, and improve efficiency of assembly.