The invention discloses acidified fly ash. The main point of a technical scheme provided by the invention is that acidified fly ash ingredients comprise fly ash, attapulgite clay, magnesium oxide, sulfuric acid, fast-dissolving sodium silicate, polyvinyl alcohol, hydroxypropyl methyl cellulose and sodium carbonate. The acidified fly ash ingredients are input into a mill for milling, and powder obtained after milling is the acidified fly ash. A production method for the acidified fly ash can prevent a chemical reaction of sulfuric acid with fast-dissolving sodium silicate, polyvinyl alcohol, hydroxypropyl methyl cellulose and sodium carbonate; after acidification of fly ash, the utilization rate of fly ash can be increased, good economic benefits, environmental benefits and social benefits are obtained, and the waste is turned into the valuable. The acidified fly ash has the characteristics of good adsorptivity, thixotropy, heat stability, plasticity, caking performance and high dry-pressing strength and is applicable to production of environmental protection materials, garden materials, building materials, foaming agents and fire-fighting products.