Abstract: Polymerized rosin epoxy resin was synthesized by esterification and ring-closing reaction of polymerized rosin and epichlorohydrin. The product was identified by FT-IR and 1H NMR spectrometries. The influencing factors of product properties were discussed emphatically. The suitable reaction conditions were as follows:mole ratio of polymerized rosin to epichlorohydrin 1:8,reaction temperature 75℃,reaction time 8h. The product had following properties:epoxy value 0.19mol/100g, viscosity (at 30℃) 30.8Pa·s, and acid value 0.2mg/g. This novel epoxy rosin had a rigid polycyclic structure, which would enrich the varieties of epoxy resin,widen the application range of rosin and increase the additional value of rosin.