Abstract: Nadic anhydride was obtained from Diels Alder reaction between cyclopentadiene and maleic anhydride.NA was used in synthesizing NA UP resin to partly replace phthalic anhydride which was usually used in synthesizing ordinary unsaturated polyester resin.Results of quality tests show that the NA UP resin compositions have good overall characteristics and a more simple technological process.Compared with the ordinary commerical UP resin,NA UP resin has better qualities and lower cost,hence it can be used to replace ordinary UP resin.