The invention relates to a new craft and a method for preparing autoclave aerated blocks. Materials are fly ash, carbide mud residue and hydrazine hydrate salt residue; sodium chloride (or the hydrazine hydrate salt residue) or/ and nitro-organic compounds are added as admixture to fasten formation of green body early strength; traditional static stopping temperature is reduced to 45 to 65 degrees from 80 to 90 degrees, which is beneficial to realize displacement 60 to 90 percents lime by the carbide mud residue. The craft and the method have the advantages that automatic production of the autoclave aerated blocks is beneficially realized because CaO content of the autoclave aerated blocks is stable and impurity content such as calcium carbonate and unburned out hydrocarbon is less; quality of the autoclave aerated blocks is improved and production cost is reduced largely.