Abstract: Activity changes of α- amylase inhibitor( α- AI) from white kidney beans during processing and digestion were investigated,which were determined after α- AI of different concentrations were treated by heat,acid,alkali and simulating gastrointestinal environment. When α- AI was at lower concentrations( < 6.00 mg / m L),a dose-dependent relationship between the concentration and the activity of α- AI was observed,while α- AI activity increased slightly with the concentration when α- AI was at higher concentrations( > 6.00 mg / m L).Heat treatment under 60 ℃ had no significant influence on α- AI activity( p > 0.05).Heat treatment over 80 ℃ greatly damaged or even destroied α- AI. Heat treatment at 70 ℃ caused an activity loss which increased with the extension of time.Acid and alkali treatment( p H3.0 ~ 10.0) significantly affected the activity of α- AI( p < 0.05),the loss of the activity was decreased with the extension of time.During digestion,α- AI activity suffered from an enormous loss and stomach accounted for the majority of the loss. Low concentration( < 8.00 mg / m L) of α- AI was nearly inactivated. Nonetheless,high concentration( > 10.00 mg / m L) of α- AI could better perform its physiological functions.