[ ${alpha}$ ]Glucosidase inhibitor is a target in the treatment of type II diabetes through the mainly inhibition of glucose levels after meals. In this study, we purified steppogenin and oxyresveratrol from the stem of Morus alba L. and examined their inhibitory activity against yeast ${alpha}$-glucosidase. Steppogenin and oxyresveratrol were inhibited yeast ${alpha}$-glucosidase in a dose dependent manner. The $IC_{50}$ activities (50% inhibition) were 34.4 and 9.3 ${mu}M$, respectively. The kinetic inhibition of steppogenin showed noncompetitive inhibition ($K_m:1.1{ imes}10^{-3}M$; $K_i:1{ imes}10^{-5}M$), meanwhile oxyresveratrol showed competitive inhibition ($K_m:4.3{ imes}10^{-3}M$; $K_i:3.4{ imes}10^{-6}M$) against yeast ${alpha}$-glucosidase. These results indicate that steppogenin and oxyresveratrol are noncompetitive and competitive inhibitors, respectively, against yeast ${alpha}$-glucosidase.