Through two-phase aqueous polymerization, amphoteric polyacrylamide (AmPAM) emulsion, as an environmental friendly flocculant for the tannery wastewater, was firstly synthesized using ammonium sulfate aqueous solution as the dispersion, using acrylamide, cationic monomer ethylene methyl propenoyl-trimethylammonium chloride (DMC), and anionic monomer acrylic acid (AA). The structure and properties of the synthesized AmPAM were characterized by means of FT-IR measurement, and the effects of various factors were studied, such as dispersing agent, dispersion medium concentration, initiator concentration, and AA/DMC feeding ratio on the intrinsic viscosity of the emulsion. The influences of pH, the AA/DMC feeding ratio, the intrinsic viscosity, and the dosage of polymer on the flocculating performance were also studied. When the weight percent of ammonium sulfate was 10.0% of emulsion total weight and dispersing agent polyvinylpyrroli-done was 1.2% and the weight percent of initiator was 4.0% of monomer total weight and m (acrylamide): m (DMC): m (AA) was 9: 5: 3, AmPAM achieved overall performance, good solubility, high stability, and application in a wide range of pH value between 4 and 10. The flocculating rate was more than 90.0%. AmPAM flocculant with both anionic group and cationic group provided a clear antipolyelectrolyte effect and a wide pH value range of the application, especially for tannery wastewater. It had not only charge neutralization and adsorption bridging role but also winding and enclosing effect among the molecules so as to flocculate and subside coarse particles of the sludge treated and dehydrate perfectly. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 518-523, 2011