A novel approach to synthesize narrow particle size distribution cationic latex particles based on styrene and butyl acrylate was proposed. The effect of monomer/water ratios, surfactant (cetyltrimethylammonium chloride) concentrations and monomer compositions on the evolution of particle size, distribution, number and morphology as a function of monomer conversion were concerned in order to confirm the optimum polymerization condition. As expected, the particle size of the ultima latex increased with monomer/water ratios and styrene contents decreased with increasing surfactant concentrations. Continue nucleation phenomena occurred when monomer/water ratio was lesser than 30/70, resulting in the number of particles gradually increased in the whole polymerization process. Combined with the previous work (Colloid and Polymer Science, 2014, 292, 519-525), it was concluded that particle coagulation easily took place in cationic emulsion polymerization of styrene. Thus, the narrow particle size distribution Downloaded by [FU Berlin] at 05:29 07 July 2015 2 cationic latexes with particle scale between 50nm and 80nm, 30wt% solid content could be prepared in a short reaction time.