The invention relates to dimmable rare earth doped lanthanum lithium molybdate fluorescent powder and a preparation method thereof. Li2CO3 powder, La2O3 powder, MoO3 powder, Dy2O3 powder and Eu2O3 powder are weighed in the mole rate being 1:(1-x):4:0.05:x, ground and stirred uniformly, and a reactant material is obtained, wherein x ranges from 0.01 to 0.17; the reactant material is calcined at 750-850 DEG C for 4-6 hours, and a reaction product is obtained; after the reaction product is cooled, the reaction product is taken out, ground and sieved, and the dimmable rare earth doped lanthanum lithium molybdate fluorescent powder is obtained. The fluorescent powder adopting a pure-phase substance structure is formed with a high-temperature solid phase method, raw materials are more widely sourced, the cost is lower, and no toxic organic matter is produced; under excitation of fixed wavelength, the developing range of the fluorescent powder can change in red and yellow light areas in a color coordinate graph by changing the doping concentration of Eu<3+> and using the energy transfer function between Dy<3+> and Eu<3+>, and the dimmable performance of the fluorescent powder is realized.