Cationic polyacrylamide, copolymerized by cationic monomer and acrylamide, is a kind of water-soluble polyelectrolyte, which is nontoxic, tasteless, soluble in water easily and insoluble in organic solvents, such as ethanol and acetone. The molecular chain is flexible, relative molecular wight is steady, ionic distribution is even. The floc forming and separation speed is fast. with firm floc and high dewatering effect