In this research, Zn-dust, ZnO, and Tin chloride were selected as catalysts for which the influence on esterification reactions of rosin and PEG was studied. Figure 2 shows the conversion percentile of the reaction using Zn-dust, ZnO, and Tin chloride. The reaction rate significantly increased with use of each catalyst. Zinc oxide was the most effective catalyst, as it resulted in the highest conversion of ester at 5 hours due to the Lewis acid performance of this catalyst. The performance of Zn-dust, however, did not yield as high a conversion rate, perhaps suggesting that the zinc cation is more readily dissolved from the oxide surface into the reaction media in comparison with metallic Zn (Hattori et al., 1994). Zinc oxide and Tin chloride are both Lewis acids, ZnO had a higher reaction rate than did Tin chloride due to ระหmoisture and temperature stability of zinc oxide. This result was consistent with results from previous studies (Tamaddon et al., 2005, Kulkarni, 2014). Therefore, ZnO was selected for esterification reaction.