In this study, the total polyphenol content, electron donating ability (EDA) and inhibitory activity of glutathione S-transferase (GST) of freeze-dried Citrus unshiu extracts were examined. The Citrus unshiu extracts was obtained from four solvents such as ethyl acetate, acetone, methyl chloride and methanol, to evaluate its functional properties. Total polyphenol contents were measured in the two different extracts, and the extracts were screened for their potential antioxidant activities using tests such as electron donating ability (EDA), glutathione S-transferase (GST). The total polyphenol contents of Citrus unshiu extracts were $928.48{\pm}1.19{\mu}g\;GAE/mL$ in ethyl acetate (EA), $886.03{\pm}0.44{\mu}g\;RE/mL$ in acetone (AC), $413.08{\pm}1.39{\mu}g\;GAE/mL$ in methylene chloride (MC), $12,648.60{\pm}0.56{\mu}g\;GAE/mL$ in methanol (MeOH), respectively. Also, the total polyphenol contents of EtOH Citrus unshiu extracts were $664.64{\pm}0.74{\mu}g\;GAE/mL$ in EA, $702.67{\pm}0.85{\mu}g\;RE/mL$ in AC, $429.64{\pm}0.61{\mu}g\;GAE/mL$ in MC, $16,108{\pm}0.73{\mu}g\;GAE/mL$ in MeOH, respectively. The total polyphenol contents were significantly difference (p<0.05) between the solvents. The electron donating ability of Citrus unshiu extracts were $62.80{\pm}0.36%$ in EA, $97.43{\pm}0.51%$ in AC, $52.20{\pm}0.30%$ in MC, $97.63{\pm}0.46%$ in MeOH, respectively. Also, the electron donating ability of EtOH Citrus unshiu extracts were $51.49{\pm}0.26%$ in EA, $63.17{\pm}0.31%$ in AC, $67.68{\pm}0.55%$ in MC, $96.18{\pm}0.41%$ in MA, respectively. The electron donating ability were significantly difference (p<0.05) between the solvents. The inhibitory activity of glutathione S-transferase in Citrus unshiu extracts were $76.22{\pm}0.65%$ in EA, $31.73{\pm}0.48%$ in MC, $97.48{\pm}0.56%$ in MeOH, respectively. Also, inhibitory activity of glutathione S-transferase in EtOH Citrus unshiu extracts were $75.54{\pm}0.55%$ in EA, $73.53{\pm}0.38%$ in MC, $48.70{\pm}0.46%$ in MeOH, respectively. The inhibitory activity of glutathione S-transferase were significantly difference (p<0.05) between the solvents. These results indicated that the Citrus unshiu extracts is a high-valued food ingredient and the extraction with methanol will be useful as a nutritional source with natural antioxidant activities. Considering high consumer demand beneficial health effects, Citrus unshiu extracts can be utilized to develop functional food health- promoting and natural antioxidant agents.