Abstract: Ceria (CeO₂) nanoparticles were successfully synthesized via a simple complex-precipitation route that employs cerium chloride as cerium source and citric acid as precipitant. The elemental analysis results of carbon, hydrogen, oxygen, and cerium in the precursors were calculated, and the results revealed that the precursors were composed of Ce(OH)₃, Ce(H₂Cit)₃, or CeCit. X-ray diffraction analysis showed that all ceria nanoparticles had a face-centered cubic structure. With the molar ratio of citric acid to Ce³⁺ (n) of 0.25 and pH of 5.5, the specific surface area of the sample reached the maximum value of 83.17 m²/g. Ceria nanoparticles were observed by scanning electron microscopy. Selected area electron diffraction patterns of several samples were obtained by transmission electron microscopy, and the crystal plane spacing of each low-exponent crystal plane was calculated. The ultraviolet (UV)–visible transmittance curve showed that ceria can absorb UV light and pass through visible light. Among all samples, the minimum average transmittance of ultraviolet radiation a (UVA) was 4.42%, and that of ultraviolet radiation b (UVB) was 1.56%.