“Water-in-water” emulsions of hydrophobically associating cationic polyacrylamide (HACPAM) with both cationic groups (methacrylatoethyl trimethyl ammonium chloride, DMC) and hydrophobic groups (n-butyl acrylate, BA) were synthesized by dispersion polymerization. The structure of the copolymer was confirmed by FTIR and 1HNMR. The prepared “water-in-water” emulsions possessed high solid content, low viscosity, good stability and solubility. An image analyzer photographed the size of the emulsion particles. The polymerization behaviors with varying concentrations of acrylamide, DMC, BA, stabilizer and reaction time were investigated. Appropriate concentrations of monomer, BA and DMC for stable dispersion system were in the scope of 10~15 wt%, 0.025 ~ 0.15 wt% and 1~ 4 wt%, respectively. The dynamic drainage experiment results show that the HACPAM “water-in-water” emulsions can be directly used as retention aid and obviously improve the retention efficiency of bleached broad-leaved pulp.