The invention discloses an iron ore tailing wall body autoclaved brick and a preparation method thereof. The autoclaved brick comprises the following components in part by weight: 70 to 90 parts of iron ore tailing, 5 to 15 parts of quicklime, 3 to 8 parts of cement and 3 to 8 parts of skeletal material; and the preparation method comprises the following steps: raw material smashing, ingredient stirring, digesting, rolling, press forming and steam press maintenance. The iron ore tailing wall body autoclaved brick prepared by the method can reach level MU 10 to 25 and has the properties of lowdensity, high intensity and the like and an industrial residue utilization ratio of as high as 80 percent; the autoclaved brick is a high-quality novel wall body material for replacing a sintered clay material; and the autoclaved brick uses the iron ore tailing as a main material, so that the environment pollution is reduced and the utilization ratio is enhanced.