The invention discloses preparation methods of an oxidized graphene / polyaniline / titanium dioxide nanocomposite and polyaniline nanometer anticorrosive paint. The preparation method of the nanocomposite comprises the steps that 1, a sodium hydroxide solution or a hartshorn is adopted as a dispersing agent, and ultrasonic exfoliation is performed on oxidized graphite to obtain oxidized graphene; 2, the oxidized graphene is added into an aniline organic sulfonic acid solution, and stirring is performed for 10-16 h to obtain an oxidized graphene / polyaniline nanocomposite; 3, nanometer titania is added into the organic sulfonic acid solution of the oxidized graphene / polyaniline nanocomposite obtained in the step 2, stirring is performed for 10-16 h, and centrifuging, washing and drying are performed in sequence to obtain the oxidized graphene / polyaniline / titanium dioxide nanocomposite. The raw materials are cheap and easy to obtain, the technology is simple and easy to control, and the obtained polyaniline nanometer anticorrosive paint is excellent in anticorrosive performance and environmentally friendly.