Abstract: In order to explore an optimized process for preparing a novel cationic emusifier，rosin，trimethylamine and epichlorohydrin as raw materials were used. The influences of reaction parameters on the esterification rate，such as reactants ratio，time，temperature and solvent by means of single-variable parameter. It was indicated that 83.4% of esterification rate could be reached under the optimal conditions as follows：ethanol as reaction solvent，n(rosin)∶n(trimethylamine)∶ n(epichlorohydrin)=1.1∶1∶1，100℃of reaction temperature and 3.5 h of reaction time. The product was characterized by IR and HNMR and the surface properties of the product were determined. The results showed that the emulsifier possessed good surface activity，and it had good emulsifying properties for rosin.