The flavonoids extracts of Pericarpium Citri Reticulatae ‘Chachi’ （PCR-CF） were extracted and purified from fresh-dried tangerine peel and Pericarpium Citri Reticulatae ‘Chachi’ （PCR-C） stored for 1 year and 10 years to study the effects of aging process on the antioxidant activities of Pericarpium Citri Reticulatae ‘Chachi’. The changes of contents of flavonoids were analyzed with HPLC. The antioxidant activities of PCR-CF were evaluated by using tert-butyl hydroperoxide （t-BHP）-induced oxidative damage in human hepatoma cells （HepG2 cells） as the model. The molecular mechanism of antioxidant activity was further explored via real-time fluorescence quantitative PCR （qRT-PCR） and Western blot. The results showed that the content of hesperidin fluctuated，but the overall trend was decreasing during the aging process of dried tangerine peel. The contents of polymethoxyflavonoids（PMFs） and total PMFs showed an increasing trend，among which the content of PCR-C10F was the highest，and the content of total PMFs reached （98.66±0.56） mg/g. Moreover，PCR-CF from different storage years significantly increased the levels of SOD and GSH and reduced the contents of MDA There was significant difference between different storage periods. The antioxidant activity of PCR-C10F was the strongest，in which the level of SOD，GSH and MDA reached （139.38±17.38） U/mg，（117.81±3.22） μmol/g and （0.39±0.03） nmol/mg，respectively. The results of correlation analyses showed that the accumulation of nobiletin was the main active component of PCR-C10F to maintain redox balance. PCR-C10F significantly up-regulated the mRNA expression levels of Nrf2 （P<0.001） and increased the expression levels of Nrf2 （P<0.05） in nuclear protein. The mRNA （P<0.001） and protein （P<0.01） expression levels of antioxidant enzymes were significantly activated，and the mRNA （P<0.001） and protein （P<0.05） expression levels of HO-1 was significantly decreased. It is indicated that the contents of PMFs in PCR-CF showed increasing trends and the antioxidant activities enhanced during aging process. PCR-C10F can protect against oxidative stress by regulating the Nrf2-ARE antioxidant signaling pathway. It will provide a theoretical basis for rational storage and quality control of PCR-C.