The autoclaved aerated concrete is prepared by using red mud-gypsum to excite blast furnace slag (BFS) and fly ash, which is of great significance to promote the resource utilization of red mud, reduce the consumption of Portland cement, and achieve CO2 reduction. The autoclaved aerated concrete with strength grade A3.5 and density grade B06 was taken as the design goal, and the influences of red mud, gypsum, BFS, and quicklime on the compressive strength of autoclaved aerated concrete were analyzed. The results show that when the mass ratio of fly ash, red mud, gypsum, BFS and quicklime is 60∶10∶3∶7∶20, the dry density and compressive strength of autoclaved aerated concrete are 623.4 kg/m3 and 3.6 MPa, respectively. The analysis of hydration products shows that the hydration product before autoclave reaction is mainly ettringite, and the hydration products after autoclaved reaction are tobermorite and katoite.