The invention discloses oil-soluble oxidized nano-graphite and a preparation method and application thereof. The oil-soluble oxidized nano-graphite is prepared through two steps: preparing graphene oxide and carrying out oil solubility modification. According to the oil-soluble oxidized nano-graphite disclosed by the invention, the problem that the dispersion of nano-graphite in an oil product is unstable is solved fundamentally, severe corrosion to metal can not be caused, and the environmental pollution is little. The oil-soluble oxidized nano-graphite disclosed by the invention serves as an anti-wear reagent at extreme pressure and is applied to hydraulic oil, and the anti-wear and anti-friction characteristics of the obtained hydraulic oil containing the oil-soluble oxidized nano-graphite are improved obviously.