The cationic polymer flotation agent PADS was synthesized by inverse emulsion polymerization with acrylamide, two methyl chloride and acrylic acid as functional material. The chemical structure of the polymer was identified by IR spectrum. In the preferred scheme, the optimal conditions were: m(AM):m(DMDAAC)=5:5, initiator dosage V-50 being 0.6%,polymerization temperature being 45 ℃，and reaction time being 4 hours. The optimization experiment of flotation agent’s dosage was conducted with luminousness as a target at 45℃.The experimental results showed that luminousness of sewage reached 92.7% when the dosage of flotation agent is 40 mg/L, which had a good flotation performance .