The invention relates to a preparation method of a sodium bismuth molybdate-tungstate nano material, and belongs to the technical field of novel nano materials. The preparation method comprises the following steps: S1, in an isopropanol solvent, solvothermal reaction between bismuth nitrate and glycerin mixed liquid is carried out to prepare bismuth glycerolate; S2, bismuth glycerolate is uniformly dispersed in a mixed aqueous solution of sodium molybdate and sodium tungstate for hydrothermal reaction, so as to obtain nano sodium bismuth molybdate-tungstate. Compared with the prior art, the preparation method has the following major advantages: sodium bismuth molybdate-tungstate prepared by adopting the preparation method is characterized in that nanocrystalline is replaced by molybdate and tungstate lattices, the defect that the heating effect of molybdate results in laser attenuation is overcome, at the same time the preparation processing equipment is simple, and the preparation process is low in temperature and small in energy consumption; the product, namely sodium bismuth molybdate (NaBi(MoW<1-x>O<4>)<2>, wherein x=0.1-0.9) prepared by adopting the preparation method is 20-50 nm in grain size, has the advantage of low sintering temperature, can be used for preparing a rare earth doping laser host material, and can also be used as a luminescent material.