Citrus peel extract was prepared using 70％ ethanol solution by two extraction conditions (20$^{circ}C$ for 72 hours and 85$^{circ}C$ for 3 hours). The effect of gamma-irradiation on the changes of physiological activity also investigated at 0, 5, 10 and 20 kGy of absorbed doses. Color characteristics, DPPH radical scavenging, tyrosinase inhibition and nitrite scavenging activities of the extracts were measured at 41$^{circ}C$ for 30 days. Color values were different by extraction methods at the initial stage, which heat-extracted sample had lower L$^$＊/ - but higher a$^$＊/ - and b$^$＊/ -values than those extracted at room temperature. Irradiation changed color of the extract lighter by increasing Hunter color L$^$＊/ - and a$^$＊/ -values. DPPH radical scavenging, tyrosinase inhibition and nitrite scavenging activities were not affected by either extraction methods or irradiation but significantly reduced by storage time. Therefore, when the cost-effective extraction methods is selected, the citrus peel extracts, which is a major byproduct in citrus processing, could be used as a functional material in various applications.