Abstract: With catechol and 1, 3- Dibromopropan as starting materials, 3, 4- Dihydro-2H-1, 5- benzodioxepin was prepared by cyclization reaction under the condition of alkaline reflux, then through Friedel- Crafts acylation to get1- ( 3, 4- dihydro-2H- 1, 5- benzodioxepin- 7- yl) ethan- 1- one. Followed by Bayer- Villiger oxidation, hydrolytic acidification and column chromate graphy separation, the final product was obtained and the yield was 28.5%.Using Infrared spectroscopy, mass spectrometry and nuclear magnetic resonance spectroscopy (1H- NMR, 13CNMR) for structure identification and characterization, the final product was identified as 3, 4- Dihydro-2H- benzob1, 4dioxepin-7-ol.Antioxidation activity in oils was evaluated.Results showed that the product had a certain antioxidation activity in both animal and vegetable oils.