Abstract: ; The processes of neucleation and growth of latex particles in emulsion polymerization for the more hydrophilic monomers such as VAc are studied. A mathematical model is proposed for stage I of emulsion polymerization of VAc. The model considers the neucleation mechanisms both by micelles and by oligomer precipitation. Meanwhile, the effects of free radical desorption from latex particles to aqueous phase and the amount of emulsifier adsorbed onto monomer droplets on the kinetics of stage I of the emulsion polymerization for VAc are taken into account. Furthermore, the prediction results by the model and the experimental data are compared and discussed.