In the process of polymer flooding, high temperature and high salinity reservoirs are often encountered. In this environment, polyacrylamide will undergo thermal degradation, shear degradation and oxidative degradation, which lead to a sharp decline in its viscosity, and fail to achieve oil displacement effect. In this paper, the molecular structure design idea was used to design the polymer structure from the primary and secondary structures of the polymer. The advanced structure and molecular chain aggregation state of the polymer were analyzed and integrated, so that the polymer formed a random micro-branched/micro-crosslinking association structure, which reduced the sensitivity of the polymer to temperature and divalent metal ions, and improved the temperature and salt resistance of the product. In order to improve the viscosity of the working fluid, the effects of AM / AMPS, branched monomer dosage, hydrophobic monomer dosage, pH value and initiator temperature on the viscosity of the polymer were studied by orthogonal test. The primary and secondary relationships of various factors on the viscosity of the polymer were determined as follows : branched monomer dosage > hydrophobic monomer dosage > AM / AMPS ratio > pH value of the system > initiator temperature.