The invention relates to a method for preparing oxide nano-materials by hydrated salt. The method is as follows: melted hydrated salt or compound melted hydrated salt is taken as solvent and reacts wiThe invention relates to a method for preparing oxide nano-materials by hydrated salt. The method is as follows: melted hydrated salt or compound melted hydrated salt is taken as solvent and reacts with metal oxides, metal halides, metal hydroxides or metal oxyacid salts under the closed reaction condition; and the oxide nano-materials are obtained by washing, separation and drying. By adopting thth metal oxides, metal halides, metal hydroxides or metal oxyacid salts under the closed reaction condition; and the oxide nano-materials are obtained by washing, separation and drying. By adopting the melted hydrated salt, the method is suitable for preparing simple binary oxides, and is more suitable for preparing complex ternary, quaternary and multi-component oxides. The method has the advantae melted hydrated salt, the method is suitable for preparing simple binary oxides, and is more suitable for preparing complex ternary, quaternary and multi-component oxides. The method has the advantages of large-scale preparation, environment protection, synthesis at low temperature, and the like, and is particularly suitable for the industrially large-scale and environmental-friendly preparationges of large-scale preparation, environment protection, synthesis at low temperature, and the like, and is particularly suitable for the industrially large-scale and environmental-friendly preparationof the oxide nano-materials. of the oxide nano-materials.