The copolymer prepared by copolymerizing with acrylamide and maleic anhydride was imidized with N,N-dimethylaminopropylamine. The obtained acrylamide-N,N-dimethylaminopropylmaleimide (ADMAPM) copolymer was then reacted with methyl iodide to yield a poly( methyl iodide quaternized acrylamide-N,N-dimethylaminopropylmaleimide) copolymer [poly(MIQADMAPM)]. Its aqueous solution properties were studied by measurements of reduced viscosity, intrinsic viscosity, and flocculation test in this study. The reduced viscosity and intrinsic viscosity of this cationic polyelectrolyte were related to the types and concentration of the added salt. "Soft" salt anions were more easily bound to the quaternary ammonium cation (R,N+) of poly(M1QADMAPM) than were "hard" salt anions. Halide anions are hard anions; consequently, hard cations were more easily attracted to halide anions and reduced the binding degree of halide anion on the quaternary ammonium group (R4Nf). The intrinsic viscosity behavior for cationic polyelectrolyte resulting from the electrostatic repulsive force of the polymer chain was contrasted with polyampholyte. The effect of various flocculants on flocculation in different pH values was accessed in this study.