For the preparation of polybutadiene latexes with suitable particle size, membrane e$$mu$</TEX>sification, which is capable of easy and uniform control of particle size, was used in this study. The parameters were the type and amount of surfactants, amount of additive and pressure. Particle size and distribution of prepared latexes were measured and compared with those of e$$mu$</TEX>sion prepared by homogenizer. To investigate the membrane e$$mu$</TEX>sification mechanism, theoretical drop size was calculated by Harkins-Brown equation. When the amount of surfactant with more than 0.2 wt%(based on DDI water) was added in the continuous phase, the stable e$$mu$</TEX>sion was prepared. Other parameters showed little relationship with particle size and distribution. In this membrane e$$mu$</TEX>sification, the essential factor for determining the particle size was the pore size of the membrane.