Abstract: The copolymer (PA) of acrylamide/sodium acrylate/cetyl dimethyl ammonium chloride and the copolymer (PB) of acrylamide/sodium acrylate/sodium 2-acrylamido-tetradecyl sulfonate were blended to form mixed solution (PA/PB system). Fixing the polymer concentration (2000 mg/L) in 5000 mg/L NaCl, based on the apparent viscosity, the optimum compound ratio (3:7) of PA to PB was obtained. At this ratio, the apparent viscosity of PA/PB system was up to 62.7 mPa•s, which was higher than that of PA or PB. Additionally, the effects of NaCl concentration, temperature, shear rate and polymer concentration on the viscosity of mixed system were investigated, which show that the PA/PB system exhibited and there were significant synergistic effects between PA and PB. On the other hand, the characteristic relaxation time (TR) and the platform area modulus (G0) were obtained by rheology measurement to study the synergistic mechanism. The result indicates that the number and structural strength of association structures of mixed system were larger than that of mono-component polymer PA or PB.