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Nanomaterials means materials in nanometer （1-100 nm） with at least one dimension in space or materials made up of units in nanometer. It possesses unique properties including surface effect, volume effect and quantum confinement effect different from bulk materials and single molecular, and can be applied in many fields such as electronics, optics, chemistry, ceramics, biology and medicine. Synthesis and preparation of nanomaterials goes deeper with the understanding of their unique properties.Nano-ferric oxide is a kind of important nonmetal inorganic material, which can be employed in the realms of pigments, catalysts, ceramics, magnetic recording materials, etc. The ferric oxide particles of many shapes, including spheres, cubes, rods, platelets and spindles, were prepared. Meanwhile, Meanwhile, various preparation methods were designed: （a）gel - sol processing; （b）forced hydrolysis processing; （c） hydrothermal processing. Compared with the other methods, hydrothermal processing has several advantages: （a） effective control of size and shape of the particles; （b） shorter preparation time; （c） fewer impurities in the final product.Single hexagonal crystalline α-Fe2O3 nano cubes were prepared by a hydrothermal process. At 130℃, the reaction was carried out in a sealed Teflon-lined autoclave employed Urotropine（（CH2）6N4） and ferric chloride（Fe2O3 ? 6H2O） as the reactants. Nanoparticles with perfect shape, narrow size distribution, and well-crystallized were prepared by the appropriate control of the temperature, time of the reaction and the concentrations of the reactants. The product is a kind of red-brown powders with particles size of 500nm. Spheres with rough surface were synthesized at 80 ℃, while pseudo cubes and some spheres were prepared at 100℃. Consequently, 130℃ is the optimal preparation temperature for the hydrothermal synthesis of α-Fe2O3 cubes. The phase composition, structure, size and morphology of the sample were determined by the techniques of XRD, TEM, and SEM. The optical property was characterized by the techniques of FTIR. Depending on the Dissolution-re-crystallization mechanism, the formation mechanism of nano cube was
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