Objective To investigate the inhibitory effect of L-arabinose and L-arabinose combined with acarbose on the activities of α-glucosidase in vitro.Methods The homogenate of α-glucosidas prepared by scraping mucosa from small intestine of rats was incubated with sucrose,maltose and α-dextrin(in a final concentration of 60 mg/ml,20 mg/ml and 20 mg/ml respectively) as optimal reaction systems to determine the inhibitory effects of L-arabinose on the activities of α-glucosidase(IC50) and the type of inhibition.Results L-arabinose inhibited the activities of α-glucosidase in a dose-dependent manner,especially selectively inhibiting the activity of sucrase in an uncompetitive manner(Ki,0.558 mg/ml) with an IC50 of 0.164 mg/ml.The combination of L-arabinose with acarbose might enhance the effect of inhibition,especially while using sucrose as substrate.Conclusion L-arabinose inhibited the activities ofα-glucosidase,especially the activities of sucrase.The combination of L-arabinose with acarbose might increase the inhibitory effect.L-Arabinose might have good prospects for practical application in sweet food.