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Based on the background that large amount of nickel slag are stacked in China, the utilization of nickel slag to prepare autoclaved aerated concrete (AAC) was researched.Calcium silicate hydrate is synthesized from nickel slag by adding cement, lime, fly ash(FA) and gypsum by hydrothermal method at 185 ℃.The products mainly consist of disordered calcium silicate hydrate, but more crystallized phase such as tobermorite forms for the presence of inorganic admixtures.The alkali cations and SO42-anions are effective accelerators and the superplasticizer triethanolamine-oleate is conducive the formation of uniform distribution of small and independent pore structure.The AAC samples were prepared on a laboratory scale with nickel slag dosage range 18%-30% when the compressive strength can be 3.9 MPa-5.7MPa.Compared with the traditional AAC, fly ash or sand was partly substituted by nickel slag in order to develop a potential technique of environment protection during the recycling of solid waste and the AAC production process.The samples of different curing stage were examined by XRD as well as SEM analyses.Results show that the main minerals in the AAC product are tobermorite, anhydrite, protoenstatite, dolomite, albite and augite, with small amount of other minerals brought in by the nickel slag.It was also suggested that most minerals in the nickel slag participated in the hydration reaction during the procuring process, and the chemical elements in them got into the structure of platy tobermorite in the subsequent autoclaving process.