To study the antioxidant activity of volatile oil and its separated parts from the peel collected in different time of Citrus reticulata ‘Dahongpao’ such as Citri Reticulatae Pericarpium (CRP) and Citri Reticulatae Pericarpium Viride (CRPV) and Fructus Citri Immaturus (FCI), and nine representative constituents of essential oil from the peel of C. reticulata Blanco. Methods: The volatile oil and its separated parts and 9 characteristic constituents were tested the antioxidant activity by using the method as FRAP (ferric reducing/antioxidant power) and ABTS (2, 2’-azino-bis (3-ethylbenzthiozoline-6)-sulphonic acid), respectively. Results: The antioxidant activity value of the volatile oil and its separated parts and 9 representative components were obtained by the method as FRAP and ABTS. Conclusion: The volatile oil and its separated parts and 9 representative constituents have the antioxidant activity in some degree. The antioxidant activities of the volatile oil from the peel collected in different time of C. reticulata ‘Dahongpao’ is listed as the following sequence: FCI=CRPV=CRP.