The invention belongs to the technical field of welding and relates to clad welding technologies, in particular to a non-halt clad welding method of an outlet gas pipeline of a draught fan of a coke oven of a chemical plant. The non-halt clad welding method of the outlet gas pipeline of the draught fan of the coke oven of the chemical plant comprises the steps of a prefabricating the pipeline, b prefabricating a reinforcing ring, c prefabricating a tee joint, d conducting clad welding, e forming openings, f, conducting connection and g installing nitrogen purging openings. Through the improvement on a traditional clad welding method, after the reinforcing ring is additionally arranged on an old pipeline, the new pipeline is welded, so that the old pipeline and the new pipeline are reliably connected into a whole, the whole weight is borne by supporting columns finally, and the technical problem that an existing large-span pipeline between supports has potential safety hazards supposedly is effectively solved. Meanwhile, through the arrangement of the reinforcing ring, an interlayer exists between the new pipeline and the old pipeline, by means of cooperation of vent holes in the reinforcing ring and the two DN25 nitrogen purging openings welded to the two ends of the communicating pipelines, the interlayer is charged with nitrogen for pressing, and then the problems that water cannot be discharged out, and the purging space is in lack are solved.