Pr-CeO2 nano-crystalline red lanthanide pigments were prepared from cerium (III) nitrate hexahydrate and praseodymium oxide by low-temperature combustion synthesis. Its ignited temperature was approximately 250°C. The prepared pigments were characterized by DSC, XRD, SEM and XPS. The results showed that the crystallite size decreases with increasing Pr mol concentration. The valence of praseodymium in the pigments and its coloring mechanism were also investigated. The trivalent Pr entered into CeO2 crystal lattice and formed Pr-CeO2 solid solution, which was based on the fluorite structure. It substituted trivalent Pr for tetravalent Ce in CeO2 crystal and was compensated by oxygen vacancies, which caused the distortion and the defection of the crystal lattice. Therefore the pigments can absorb the light with the wavelength of approximate 600nm and present the red tonality.