Fresh onions were extracted by two methods of conventional extraction(CE) and microwave assisted extraction(MAE) under different extraction conditions. Onion extracts obtained by CE and MAE were examined in oleoresin yield and physiological activities. The optimal extraction time of MAE was about 5 minutes, whereas that of CE was 2 hours. Therefore extraction time was shortened drastically by MAE but there was no significance in oleolesin yield. The electron donating abilities also showed negligible difference between two extracts obtained by CE and MAE, and 45% level in CE and 50% level in MAE. The nitrite scavenging effect was diminished while pH was increasing, and showed a high elimination effect over 85% at pH 1.2. The tyrosinase inhibitory effect was 20% level in both CE and MAE when water was used and 40% level when ethyl alcohol was used. The angiotensin I converting enzyme inhibitory effect showed higher activity with 70% level in MAE than 60% level in CE. The pyruvic acid content was 6.8 and 6.4 moles per 1g of fresh onion by CE and MAE when water was used, and was 4.3 and 5.6 moles by CE and MAE when ethyl alcohol was used.