Aiming at the problem existing in the current method for repairing a mountain city pipeline and the inadaptability of a method for repairing a drainage pipeline with large pipe diameter, the invention provides a steel-pipe-insertion local strengthening trenchless repair method for a drainage pipeline with large pipe diameter. In the method, one steel pipe is inserted into a pipeline to be repaired at a distance, and the upper side of the middle of a steel casing pipe is additionally provided with a crescent rib to improve the strength. When used by matching with a coating repair method, the method can be used for non-structural repair of the pipeline and can also be used for structural repair of the pipeline. The method is more convenient for construction without large-scale construction equipment, materials are saved, and the repair price is cheep. The method is suitable for repairing the pipeline with a pipe diameter of more than 800mm.