The epoxy esters was prepared by linoleic acid and epoxy resin E-51 after ring-opening reaction, then using it to replace part of the polyols involved in the reaction. After neutralization with amine, an epoxy modified water-alkyd resin was prepared. The structure of the product was investigated characterized by FTIR. We discussed the synthesis process of epoxy esters, and in-depth analysis of the epoxy ester dosage on the performance of the resin and its film. The results showed that the epoxy ester was obtained under the condition as followed: reaction temperature 110 ?C, reaction time 4h, tetrabutylammonium bromide dosage 8‰, acid value 13.3 mgKOH?g-1. When the epoxy ester content was 10%, the overall performance of the resin and the paint film was optimal, and the thermal stability of the waterborne alkyd resin paint film after epoxy modification was significantly improved.