The　DCPD　(dicyclopentadiene)-modified　unsaturated　polyeaster　by　semi-condensation　polymerization　method　was　studied.　The　results　show　that　the　optimal　conditions　of　synthesis　reaction　are　as　follows:　the　total　anhydride/propylene　glycal/DCPD　ratio　is　1:1.　1:0.10-0.15,　the　temperature　of　addition　reactions　is　120-140°C,　the　acid　value　of　the　system　is　120-140　mgKOH/g　when　dropping　DCPD　and　the　time　of　addition　reaction　is　about　2　hours.