Abstract： Objective To investigate the protective effects of alpha-lipoie acid (ALA) against beta-cell damage in streptozotocin (STZ)-induced diabetes in rats. Methods Thirty SD rats were randomly divided into three groups: normal control (NC) group, STZ group and ALA + STZ group, with 10 rats in each group. mg/kg, intraperitoneal injection), till the end of the study (4 weeks later). Blood glucose were measured every 3 days after STZ injection. Malondialdehyde (MDA) and reduced glutathione (GSH) levels were measured in pancreatic homogenates. Pancreatic beta-cells were examined by immunohistocbemical methods, Results STZ induced a significant increase of the level of blood glucose. Body weight of rats in ALA + STZ group was (341±26)g, which significantly lower than (368±3)g in NC group, and high than (301±2)g in STZ group with stas(P < 0. 05). Meanwhile the MDA levels in STZ group and NC group were(1.22 ± 0. 14) and(0.57 ± 0.04)nmoL/mg prot, respectively, and there was significant difference between the two groups (P < 0.05) ; the GSH levels in STZ group and NC group were(16.54 ± 1.10) and(25.46 ± 0.62) mg/g prot (P < 0.05), respectively; degeneration of islet cells and decreased blood glucose were observed in STZ + ALA-pretreated rats; MDA level in pancreatic homogenates was(0.72 ± 0. 23)nmoL/mg prot, which was significantly lower than that in STZ group (P < 0.05) ; the GSH level was (35.33 ± 2.66) mg/g prot, which was significantly higher than that in STZ group (P < 0.05) ; increased staining of insulin and preservation of islet ceils functions were more obvious in the STZ + ALA-pretreated rats. Conclusions ALA exerted its protective effect through reducing the oxidative stress and preserving pancreatic beta-cell integrity.