Abstract: This is an essay in the field of ceramics and composites. The iron tailings are replaced with river sand to prepare autoclaved concrete. The influence of cement dosage, fly ash dosage, iron tailing sand dosage and water reducing agent dosage on the fluidity and compressive strength of autoclaved concrete is analyzed. The concrete is autoclaved and cured. The hydration mechanism of concrete under different autoclave time is analyzed. The results show that considering economy and sample strength, as cement dosage of 551 kg/m³, iron tailing sand dosage of 20%, fly ash dosage of 225 kg/m³ and water reducing agent dosage of 0.20% is selected. Under the action of the above comprehensive indicators, the compressive strength of concrete is determined to be 61.13 MPa. The longer the autoclave time is, the more active the mineral components in the iron tailings will be stimulated, and the hydration reaction inside the concrete will be more thorough. The more crystals and gels are formed, which effectively improves the strength of concrete.