Abstract: Nitric acid solution of cerium(Ⅲ) nitrate was used as raw material, and massive solid products could be obtained after heated by microwave. After adding formic acid, solid powder precursor with good dispersion could be generated by heating. The product of each step was determined by XRD, and the particle size and morphology of the products before and after calcination were characterized. The results show that the massive cerium(Ⅲ) nitrate dihydrate is obtained after heated by microwave, and the product is cerium formate with a rodlike structure after the reaction of formic acid with it. When the concentration of formic acid is 16-20 mol/L and the molar ratio of HCOOH/Ce is 18, the powders with more uniform particle size can be obtained. Cerium formate obtained under 16 mol/L and 20 mol/L formic acid are calcined into cerium dioxide, with the same morphology and similar particle size distribution range as the particles before calcination, but fine particles smaller than 0.30 μm will be generated.