The invention provides a method for replacing a tuyere-cooler casing of a blast furnace. The method comprises the following steps: selecting at least two preset points on the tube wall, far away from connected and overlapped sections of the tuyere-cooler casting and a flange base, of the tuyere-cooler casting; breaking open the tube wall of the tuyere-cooler casting by adopting a melting cutting way along the busbar direction of the tuyere-cooler casting by taking the preset points as starting points so as to cut the tube wall of the tuyere-cooler casting between the preset points and the inner end of the tuyere-cooler casting furnace into a plurality of parts, wherein the area of the end face of each part is smaller than 1/2 of that of the end face of the tuyere-cooler casting, and a space is formed at least between two of the parts through melting; and dismounting the tuyere-cooler casting from the blast furnace in a direction far away from the blast furnace. By adopting the method provided by the invention, the tuyere-cooler casting can be rapidly broken open without damaging a flange base, thus the tuyere-cooler casting is rapidly dismounted and the time for replacing the tuyere-cooler casting is shortened.