Abstract: An immobilized nano-photocatalyst H₄SiW₁₂O₄₀/Bi₂WO₆ was quickly prepared by the supercritical hydrothermal synthesis method. The properties, morphology and structure of the prepared catalysts were investigated and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), and transmission electron microscope (TEM) and BET, respectively. The photocatalytic denitrification properties were evaluated by using the model oil with 15 mg/g pyridine. The results show that the photocatalyst is the self-assembly three-dimensional spherical structure by two-dimensional nano-flakes, and the relationship between Bi₂WO₆ and H₄SiW₁₂O₄₀ is not a simple solid loading, but is a new crystal under the condition of supercritical water. It is because the existence of this kind of crystal that the H₄SiW₁₂O₄₀ is firmly fixed on the Bi₂WO₆ photocatalyst and the photocatalytic activity and service life of H₄SiW₁₂O₄₀/Bi₂WO₆ photocatalyst are improved. In view of the contradiction between the preparation period of photocatalyst and the crystal development, the supercritical hydrothermal technology and the photocatalyst template-oriented synthesis technology are organically combined to obtain the H₄SiW₁₂O₄₀/Bi₂WO₆ photocatalyst with good crystal heterostructure and greatly shorten the preparation period of the photocatalyst, greatly reduce the preparation cost of the catalyst and overcome the main contradiction of the industrialized application of the photocatalyst. The nitrogen removal efficiency of the prepared H₄SiW₁₂O₄₀/Bi₂WO₆ photocatalyst for light oil is as high as 97%.