The invention relates to a rare earth sulfur oxide colorant and a preparation method thereof. The preparation method comprises the following steps: firstly performing a roasting reaction under the temperature condition of 500-1500 DEG C by adopting a rare earth compound, sulfur, an alkali metal compound and solid carbon according to an appropriate weight ratio to obtain a rare earth sulfur oxide colorant initial product; and adding one or more selected from the group consisting of a stearate, a basic carbonate, a dihydrogen phosphate, a silicate, a zirconium salt and tetraethyl orthosilicate into the rare earth sulfur oxide colorant initial product, and performing post-treatment to finally obtain the rare earth sulfur oxide colorant sample. According to the colorant and method provided bythe invention, a dense oxide coating layer is formed at the surface of the rare earth sulfur oxide colorant sample, the stable oxide can effectively improve the thermal stability and vividness of therare earth sulfur oxide colorant, and colorants with different colors can be obtained by adjusting a ratio of a rare earth element to sulfur to oxygen in the rare earth sulfur oxide; and the process is simple to operate, has low costs, does not use toxic or harmful gases in the production process, and has high production efficiency.