Firstly，polymerizable surfactants DC12MAAC with long hydrophobic chains were synthesized，and their structures were confirmed by IR and 1 H NMR analysis. Next，the copolymer P［DPM/DC12MAAC］was synthesized by copolymerization of dimethylaminopropyl methacrylamide（DPM）with the DC12MAAC. Using weight increment of iron sheet per unit surface area and turbidity reduction rate as evaluation indexes，the reaction conditions of copolymerization were optimized by single factor method. The optimum reaction conditions were obtained as follows，the monomer concentration was 50%，the monomer ratio of DPM to DC12MAAC was 100∶2，initiator concentration was 0.8% ，the reaction time was 6 h and the reaction temperature 60℃ . The evaluation of flocculation effect of P［DPM/C12DMAAC］showed that the highest turbidity reduction rate was 99.53%，the lowest weight gain of iron sheet per unit surface area was 43.02 g/m2，which could reduce flocs by 74.90%，composed of the result of flocculant treatment in oilfield，being of 171.39 g/m2. P［DPM/DC12MAAC］had good surface and interface activity. It was speculated that the principle of clean water was to destroy the diffusion double electron layer of oil droplets through electrostatic adsorption to neutralize the negative surface charge.