The embodiment of the invention discloses a high-temperature corrosive diagnosing method and device of a boiler side wall water wall. The method comprises the following steps that according to a burner corresponding to a design parameter, burning and wall adherent atmosphere measurement are conducted on a boiler device; and boiler side wall smoke component distribution after wall adherent atmosphere measurement is obtained, so that the high-temperature corrosive condition of the boiler side wall water wall is determined subsequently according to boiler side wall smoke component distribution. The technical problem that due to high-temperature corrosion of a side wall water wall of an existing supercritical opposed burning boiler, insecurity is caused is solved.