The invention discloses a temperature-resistant anti-salt oil-displacing polymer as well as a preparation method and application thereof. The preparation method of the temperature-resistant anti-saltoil-displacing polymer comprises the following steps: dispersing modified nano cellulose and water soluble monomers in water, then adding ethylene diamine tetraacetic acid, ceric ammonium nitrate, tetramethylethylenediamine, AIBA, tert-butyl hydroperoxide and hydrogen peroxide, and reacting; and after the reaction is ended, adjusting a pH value of a reaction system to 8 to 9, and performing the aging, thus obtaining the temperature-resistant anti-salt oil-displacing polymer. The modified nano cellulose has good dispersing performance and high-temperature stability; by virtue of high interaction effect between the modified nano cellulose and polymers, the rigidity of polymer molecules can be improved, and a good polymer intermolecular network structure can be formed, thereby producing excellent performance such as temperature resistance, salt resistance, aging resistance and the like.