Abstract: Oil in water(O/W) natural rosin emulsion was prepared by the method of normal pressure phase inversion emulsification with natural rosin as raw material and ONIST APS-350 as emulsifter. The influences of emulsifier dosage, initial emulsification temperature, oil-water ratio(the mass ratio of rosin and water) and stirring speed on the particle size distribution of O/W natural rosin emulsion were investigated, and then the response surface method(RSM) was used to simulate and optimize the process parameters. The results showed that the optimum parameters were determined as follows:stirring speed 500 r/min, emulsifier dosage 9.95%, temperature 112℃, and oil-water ratio 10:31. Under these conditions, the average particle size of emulsion was 131.1nm, the emulsion was not stratified by centrifugal force and not stratified for 3 months. The results of TEM showed that the particles had core-shell structure, and the particle size was consistent with the experimental value.