A method for the preparing pure, thermally stable and high surface area ceria is described, wherein the ceria maintains a surface area of 12 m.sup.2/g after calcination at 980.degree. C. in air for 4 hours. In the method, an aqueous solution containing Ce.sup.3+, Mg.sup.2+, organic acid and organic polymer is prepared and then evaporated to obtain a gel. The gel is calcined to obtain a mixed oxide, and then MgO is leached from the mixed oxide with a solvent to obtain raw ceria. The raw ceria is then washed, filtered and dried to obtain a ceria product.