Abstract: Due to poor salt tolerance and heat resistance of the partially hydrolyzed acryl amide in high temperature and high salinity reservoirs, and the poor ability of shear, the Copolymers (AM-AA-AMC16S) is prepared by aqueous solution polymerization, It is investigated that effect of the initiation temperature, the concentration of ammonia water and the urea on molecular weight,and content of the surfactant on the filtering factor. Furthermore, investigating property of the thermally stability of the copolymers. The result shows that the aqueous soluble polymer has high molecular, when the initiation temperature is 11℃,content of the ammonia water and the urea is 0.001 mg/L and 0.0002 mol/L, the copolymer has good thermal stability. It can meet the needs of polymer flooding in the reservoir of high temperature and high salinity formation.