Abstract: A series of poly (acrylamide - Diallyl dimethyl ammonium chloride) copolymer were prepared by inverse microemulsion polymerization with aqueous solutions of AM and DMDAAC as the water phase, Span80 / Tween60 / Isopar M solution as the oil phase, and (NH4)2S2O8/NaHSO3 as oxidation-reduction initiator for polymerization. The copolymer structure, residual acrylamide monomer and surface morphology were analyzed by infrared spectroscopy (IR), high performance liquid chromatography (HPLC) and scanning electron microscopy (SEM), respectively. It was found that stable and transparent microemulsion was obtained at 40 ℃ when the HLB value of compound emulsifier was 8.5, the mass ratio of AM to DMDAAC was 8∶2, the mass percentage of initiator was 0.7% relative to total monomers and the mass content of emulsifier was 25% in oil phase. No monomer residue was found in the cationic polyacrylamide and the cationic degrees of copolymer could reach 30%