The invention discloses iron oxide red and a preparation method thereof. The preparation method comprises the steps of using a gallium extraction resin eluant as a raw material, treating the gallium extraction resin eluant and obtaining the iron oxide red. The gallium extraction resin eluant produced in an aluminum oxide production process by a pulverized fuel ash acid method is subjected to the treatment such as purification, refining, precipitation and burning, and a high index iron oxide red product meeting a national primary standard and having iron oxide content up to 99.3wt% is obtained. Therefore, the method shortens a technological flow, saves energy sources, produces a better economic benefit, opens up a new efficient treatment approach for composing the complicated gallium extraction resin eluant, has an important significance in boosting gallium extraction, realizes waste utilization and also provides a new preparation approach for producing the iron oxide red at the same time.