Waterborne emulsions of lightly sulfonated polystyrene ionomer(SPS) were prepared by neutralizatioin with ammonia liquor and addition of water.The principle of emulsification was explained.The aggregated structure of SPS chains in organic solvents was discussed.SPS molecule chains can form a type of microionic lattice.The variations of the conductivity and viscosity of SPS ionomer solution during the emulsification process were studied.The emulsification process and phase inversion were characterized by using the variation of conductivity and viscosity.The emulsification process included the dissociation of the microionic lattices and aggregation of the hydrophobic segments.The aggregated structure of SPS ionomer chains in solvents varied with the variation of polar of solvents were studied and affected the emulsification process.The mechanism of the phase inversion was discussed.The effects of solvent polarity and ionic contents on the emulsification process were studied. The stability of emulsion were much affected by the ionic contents.The particle size increased with the decrease in ionic contents.