The invention provides a preparation method of boron-doped graphene/TiO2 nanorod photocatalytic material. The method comprises the following steps of preparing graphene oxide by a method disclosed in pages from 4806 to 4814 in the volume 4 in 2010 of nanometer periodical of the American chemical society; weighing 8-80mg of graphene oxide, feeding 15-25ml of deionized water and carrying out ultrasonic dispersion to obtain graphene oxide dispersion liquid; feeding sodium borohydride and titanium trichloride solution into the graphene oxide dispersion liquid, stirring and then carrying out a hydrothermal reaction to obtain precipitate; and washing the precipitate, carrying out vacuum drying, and grinding the product into uniform powder to obtain the boron-doped graphene/TiO2 nanorod composite photocatalytic material. After the method is adopted, titanium dioxide can be well loaded on boron-doped graphene, the photocatalytic activity of the composite material is improved, harmful gases such as nitrogen oxide and nitrogen dioxide can be chemically adsorbed, and the harmful gases can be well adsorbed and decomposed on the surface of the graphene.