The invention discloses a reduced graphene oxide/nano TiO2 composite demulsifier and a preparation method thereof. The preparation method comprises the following steps: preparing graphene oxide with carboxyl and hydroxyl on the surface; performing surface modification with nano TiO2 generated by in-situ hydrolysis of an organic titanium precursor on graphene oxide, and then carrying out hydrothermal reduction to obtain the reduced graphene oxide/nano TiO2 composite demulsifier. The invention also provides the reduced graphene oxide/nano TiO2 composite demulsifier obtained by the method. The demulsifier provided by the invention has the characteristics of high efficiency and environmental protection, does not pollute the environment, can be suitable for neutral and acidic conditions, and has high salt tolerance; and meanwhile, the demulsifier can be transferred into an oil phase after demulsification, so that the demulsifier is prevented from staying in a water phase to influence subsequent use of the water phase.