The invention relates to treatment fluid for removing the mildew in a dry plate or film, which is prepared by the following components in accordance with the weight percentage of: one percent to three percent of organic acid, one percent to ten percent of inorganic acid, one percent to three percent of reducing agent, and eighty-five percent to ninety-five percent of de-ionized water, wherein, the organic acid is oxalic acid and/or acetic acid, and the inorganic acid is nitric acid, hydrochloric acid or sulfuric acid. The invention also relates to a method which adopts the treatment fluid for handling the mildew in the dry plate or film. By using the treatment fluid and the processing method provided by the invention, the mildew type defects of the dry plate or film can be removed in a shorter period, however, the graphics layer or emulsion layer of the dry plate or film is not affected, the defects such as scratching, graphic abnormality, surface contamination and the like on the dry plate or film due to manual handling are overcome, and the scrap rate of the dry plate or film, which is caused by impossible repairing or failed manual repair of the defects is reduced.