Abstract: Sweet oranges ［Citrus sinensis (L.) Osb.］ were stored in ultra lowoxygen condition (0.3% O2 + 0.0 %CO2) at 5 ℃ and in normal air condition at 5 ℃ and 10 ℃ to investigate the contents of volatile compounds in fruit tissue, in order to evaluate the fruit quality and physiological disorder in ultra lowoxygen atmosphere storage.Ultra low O２ treatment significantly stimulated the accumulation of ethanol and acetaldehyde in the fruits, although their concentrations in control fruits increased considerably with storage time.Ethanol contents reached 519.8 μg/kg in peel and 1 547.1 μg/kg in juice,respectively,after 30 days in ultra lowoxygen condition, which were about 83 times higher than those in control fruits. Ultra low O2 treatment had no significant effect on soluble solids content, pH and titratable acidity. When ethanol content in juice was below 1 000 μg/kg, the fruit flavour and quality were normal.