With phthalic anhydride wastes as raw material, adopts the method of sublimation to extract maleic acid and prepare high pure transparent white acicular crystal fumaric acid, and meanwhile studies the effects of the reaction temperature and time on the high-purity fumaric acid yield. The experimental results showed that: at the set temperature and time, the yield of fumaric acid increased with the reaction temperature or heating time increasing, and at the reaction temperature of 220 ℃ and the heating time for 20 min, obtained the highest fumaric acid yield of 88.8%. The product purity was determined by HPLC, the results show that the purity of the product is as high as 99.99%; and in the infrared spectra, the product appeared trans olefin characteristic absorption peak in the 925 cm-1 location and confirmed the product of fumaric acid. The experimental results at the best experiment condition show that: the preparation of fumaric acid from industrial wastes by sublimation method not only has higher yield but also has good experimental reproducibility. Keywords ：fumaric acid；sublimation method；maleic acid；phthalic anhydride waste