The invention discloses a method for preparing ferrate solution by utilizing red mud, which comprises the following steps: adopting waste red mud generated during the industrial production of aluminum oxide as raw materials; firstly adding strong alkaline solution into a reactor and simultaneously inputting red mud powder after being dried to be uniformly agitated; heating and boiling to the paste state, wherein the weight ratio of the red mud and the strong alkaline solution is 1:2 to 6; then adding NaC1O solution with 8 to 15 percent of available chlorine; heating the under the normal pressure; reacting at the temperature of 35 to 90 DEG C, wherein the reaction time is 5 to 30 minutes; fully agitating while heating, wherein the weight ratio of the red mud and the NaClO solution added is1:2 to 8; after the completion of the reaction, centrifuging or filtering reaction solution; and obtaining the ferrate solution after the reaction solution is treated. The invention has the advantages of simple method and low cost, and provides a novel method for the comprehensive utilization of the red mud, so that wastes can be resourced, the environmental pollution is reduced, the requirementsof recycling economy are satisfied, and both the economic benefit and the environmental and the social benefits are obtained.