The invention discloses a polymer suitable for high temperature and high salinity oil deposits and a preparation method of the polymer. The chemical structural formula of the polymer is shown in the description. The polymer has a net structure and is capable of effectively inhibiting high temperature and oxidative degradation, thus effectively improving salt resistance and enhancing viscosity increasing capacity. After the polymer disclosed by the invention is introduced into a ternary compound system, the ternary compound system has good chemical stability and excellent salt resistance under high temperature and high salinity conditions, the interfacial tension of crude oil/formation water is reduced to ultra low under weak base and sodium carbonate conditions, the recovery ratio can be increased by 20% or more, and thus the obtained ternary compound system can be applied to extremely high temperature and high mineralized oil deposits.