Colorant and preparation method thereof

The invention discloses a rare earth sulfide colorant and a preparation method thereof. The chemical formula of the rare earth sulfide colorant is RE2-2xS3-3x.2y[REPO4], wherein RE is one or more of La, Ce, Pr, Nd and Sm, and the ratio of y to x is 0.001-0.65. The invention further discloses application of a phosphorous compound to the improvement of color brightness of the rare earth sulfide colorant.