The water-soluble cationic terpolymer of acrylamide was prepared by the aqueous solution polymerization with (2-methacryloyloxyethyl) trimethyl ammoniumchloride (DMC) and dimethyldiallylammonium(DMDAAC) as cationic monomers, persulphate/bisulphite and the water-soluble azo-compound as the hybrid initiators. The structure and composition of the cationic terpolymer were characterized by Fourier TransformInfra-Red, 1H-NMR and Thermogravimetry. Through discussing the effects of terpolymer concentration, shear rate, pH and concentration of added salts on apparent viscosity of terpolymer solution, the rheological properties of terpolymer solution were studied in details. The results indicated that the cationic polymer was P(AM/DMC/DMDAAC) possessing excellent thermal stability. The apparent viscosity of polymer solution increased with increasing terpolymer concentration and was sensitive to pH. However, the apparent viscosity decreased with increasing shear rate, and the shear thinning behavior was obviously irreversible. The terpolymer solution displayed anti-polyelectrolyte characteristics in added salts solution.