In this study, the highest oil yield of kumquat peel essential oil extraction of 3.89±0.03% was achieved under the supercritical carbon dioxide (SC-CO2) extraction condition including 250 bars, 50°C, fluid rate of 20 g/min and 120 min of extraction. Limonene comprising 39.25% was the main component of the oil. It showed 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) cation radical (ABTS•+) scavenging activity and ferric reducing antioxidant power (FRAP) value of 25.29±0.17mM Trolox equivalent (mM TE)/g dry weight and 6.25±0.15 mM TE/g dry weight, 4565 and 4623 folds lower than those of vitamin C, respectively. Inhibition zone diameter (IZD) of pure oil equaled to that of (i) 9.2 µg/mL Ampicillin solution against Bacillus subtilis, (ii) 23.4 µg/mL Ampicillin solution against Staphylococcus aureus, (iii) 7.2 µg/mL Streptomycin solution against Klebsiella pneumoniae, (iv) 35.1 µg/mL Amikacin solution against Pseudomonas aeruginosa, and (v) 37.7 µg/mL Amikacin solution against Proteus mirabilis. Meanwhile, minimal inhibitory concentration (MIC) value of the oil was 5 mg/mL for B. subtilis and 10 mg/mL for the rest bacteria.