Abstract: According to the Mannich reaction，initiators were added at appropriate temperatures to acrylamide (AM) and dimethylamino ethyl acrylate methyl chloride (DAC) to initiate a free-radical co-reaction between AM and DAC and then to prepare cationic polyacrylamide （CPAM ）macromolecular flocculant. The influences of such factors，as total concentration of monomers，use of initiators，copolymerization temperature，pH value and solubilizer on the main characteristics of CPAM in the process of the co-reaction were investigated，and the optimal reaction conditions were obtained as follows：copolymerization temperature 35 ℃，total concentration of monomers 20%，relative molar ratio 6∶1，composite initiator 0.08%，pH value 7，solubilizer 2 %，time of ventilating nitrogen 15min，and reaction time 5h. Under the conditions above，a CPAM product with good solubility and flocculation property，low combined costs and molecular weight of 3.00×106 was synthesized.