The objective of this research was to evaluate the inhibitory activities of phenolic compounds isolated from Morusalbacv.Kuksangagainstα-amylase and α-glucosidase. The total phenolics content of extracts from Morusalbacv.Kuksangwas 9.7±0.2 mg/g soluble in water and 14.3±0.2 mg/g soluble in ethanol. The inhibitory activity of the water extracts (200 μg/mL phenolics) against α-amylase and α-glucosidase was determined as 93.8% and 48.7% respectively. The purification of inhibitory compounds was carried out by Sephadex LH-20 and MCI-gel CHP-20 column chromatography using a gradient elution procedure of increasing ethanol in H2O. The quercetin was confirmed to be the chemical structure of the inhibitory compound agains α-amylase and α-glucosidase by spectroscopic analysis of FAB-MS, NMR and IR spectrum.