The invention provides a preparation method of nitrogen-doped silicon-aluminum immobilized TiO2 porous ceramic. The preparation method comprises the steps of: carrying out reaction with water-soluble inorganic silicon salt as a silicon source, water-soluble inorganic titanium salt as a titanium source, water-soluble inorganic aluminum salt as an aluminum source, urea as a nitrogen source and cetyl trimethyl ammonium bromide as a template agent to obtain a suspension D, transferring the suspension to a hydrothermal kettle, carrying out hydrothermal reaction, after hydrothermal reaction is finished, washing, carrying out suction filtering to obtain filter mud, granulating and shaping the filter mud, then drying to obtain nitrogen-doped silicon-aluminum immobilized TiO2 precursor, and sintering the nitrogen-doped silicon-aluminum immobilized TiO2 precursor to obtain the nitrogen-doped silicon-aluminum immobilized TiO2 porous ceramic. According to the invention, urea is used as the nitrogen source, under hydrothermal high-temperature and high-pressure conditions, N-H bond in urea can replace oxygen in Ti-O to firmly bond in a chemical bond form, thus effective doping is achieved; and in addition, lattice distortion generated due to nitrogen entering TiO2 lattice can broaden photoresponse range of TiO2 and increase photocatalysis activity under visible light.