The polyphenol oxidase(PPO) inactivation by microwave irradiation was compared with steam blanching and hot-water blanching.The rudimental conditions of enzyme inactivation by microwave were investigated.The results showed that enzyme inactivation was much faster and the quality of banana slice was better by microwave irradiation than by steam blanching and hot-water blanching.When the power density of microwave was 4w/g,the activity of PPO could be decreased to below 5% in 5 min.The effect of thickness of banana slice on enzyme inactivation by microwave was insignificant,and the banana could be treated by monolayer or double deck under microwave irradiation.