Antioxidant components in Camellia nitidissima Chi flower flavonoids (Cnfe) were studied with an on-line screening method based on iron binding-HPLC,and off-line antioxidant methods (DPPH and ABTS).The compounds with potential antioxidant effects in Cnfe was identified using a Time of Flight Mass Spectrometry (TOF/MS) method.In addition,the antioxidant activity in vivo of Cnfe was also investigated.Nine compounds in the Cnfe were found to possess the potential antioxidant activity.They were identified as epicatechin,procyanidin dimer,procyanidin C1,procyanidin tetramer,6-C-pentosyl-8-C-hexosyl apigenin,rutin and quercetin-glucoside.The results of in vivo antioxidant activity showed that Cnfe significantly increased the content of catalase (60.47±2.80 U/mg),glutathione peroxidase (649.10±51.50 U/mg) and total superoxide dismutase (69.91±4.56 U/mg),and reduced the content of malondialdehyde (1.83±0.16 nmol/mg).Thus Cnfe improved the oxidative stress in rats.