Allochroic effect of rare-earth molybdate materials is related to the reflection spectrum and the power distribution of illuminants. Based on the chromaticity, the power distribution of four standard illuminants (i.e., D65, A, F2 and F11) were compared for constructing the illuminant difference functions (IDF), indicating that a significant allochroic effect of the materials usually occurs between two illuminants with a great difference in the power distributions. The allochroic effect appears when the minimum reflectivity is near asharp peak of IDF, while the color difference is small asthe minimum reflectivity isfar away from the sharp peak. Rare-earth ions with a potential allochroic effect were selected based on the atomic characteristic absorption spectra, and rare-earth molybdate materials synthesized via solid-state reaction were used for the related experimental validation.