Inhibiting the activity of alpha-glucosidase and glycosylation of protein is an important way to treat diabetes mellitus and its complications. In this study, we investigated the anti-alpha-glucosidase activity, anti-glycation potential and structure of proanthocyanidins from fruit pulp of Clausena lansium (Lour.) Skeels. C. lansium fruit pulp proanthocyanidins showed a remarkable inhibition against alpha-glucosidase activity with IC50 vaule of 0.26 +/- 0.01 mu g/mL in a competitive manner, and quenched the fluorescence of alpha-glucosidase by forming proanthocyanidin-alpha-glucosidase complex. Furthermore, compared to positive agent aminoguanidine (AG), the proanthocyanidins were the more significant inhibitors of non-enzymatic glycation by strongly inhibiting the formation of alpha-dicarbonyl compounds and advanced glycation end products. In addition, the structure of the proanthocyanidins was characterized in detail. These compounds were mainly composed of prodelphinidins, and their gallates. The main extender units, gallocatechin epigallocatechin and their gallates, were critical factor of the strong anti-alpha-glucosidase and anti-glycation activity. Therefore, this study authenticated a efficient alpha-glucosidase inhibitors and antiglycation agents, which would contribute to the development of anti-diabetic drug.