The invention discloses a temperature-resistant and salt-resistant oil displacing polymer containing nano particles. A preparation method of the polymer comprises the following steps that 1, the surface of nanosilicon dioxide is inoculated with amidogen, and modified nanosilicon dioxide is obtained; 2, modified nanosilicon dioxide, water-soluble monomers and water are mixed, the pH of the mixed system is adjusted to range from 4 to 8, nanosilicon dioxide is completely dispersed in the water, disodium edetate dehydrate, ferrous sulfate and tetramethylethylenediamine are added into the mixed system obtained after the pH is adjusted, then azobis(isobutylamidine hydrochloride), ammonium persulfate and hydrogen peroxide are added, the reaction I is carried out in the nitrogen atmosphere, the reaction II is carried out after temperature rise, the pH of the reaction product of the reaction II is adjusted to range from 8 to 9, constant-temperature ageing is carried out, and the polymer can be obtained after drying and smashing are carried out. The dispersing performance and high temperature stability of modified nanosilicon dioxide are utilized, through interaction between nanosilicon dioxide and the polymer, the rigidity of polymer molecules is improved, a network structure among the polymer molecules is formed, and excellent temperature resisting, salt resisting and ageing resisting performance and the like are generated.