Abstract: The active oxygen metabolism and some physiological changes in postharvested Citrus sinensis Osbeck CV．Jincheng grown on different hilllands were studied．The results show that the changing curves of active oxygen and the superoxide dismutase(SOD)activity in the postharvested citrus rise in the first and then fall，and the peak value of SOD activity is fallowing to that of the active oxygen．Both the active oxygen production rate and the SOD，peroxidase(POD) and catalase(CAT)activities of the peel and juice sac are significantly decreased when stored in the lower temperature，but the activities of SOD and CAT are relatively higher．The active oxygen metabolism is significantly related to the plant borlrlones，content of malondialdehyde(MDA)，cell electrolyte leakage and quality of fruits．