Objective To investigate the hypoglycemic effects of Laminaria japonica (L. japonica) on diabetic model induced by alloxan in rats. Methods Sixty healthy female rats were used to establish diabetic models by injecting alloxan peritoneally, and L.japonica was applied as raw materials for potential marine drugs.The levels of fasting blood glucose (FBG) were detected by automatic blood glucose device. Enzyme linkedimmunoabsorbant assay was applied to determine the insulin level in serum. The shape and structure of isletcells were observed with histopathological staining, and the expression of superoxide dismutase (SOD) and inducible nitric oxide synthase (iNOS) in islet cells were detected by immunohistochemical technique. Results After the treatment, the levels of FBG of L.japonica treated group B [(9.37±1.70) mmol/LandC (9.18±1.65 ) mmol/L, F= 32.81, q=6.35～11.72, P<0.05 ] reduced, while the serum levels of insulin in treated group A, Band C (0.0378±0.0026, 0.0378±0.0027, 0.0367±0.0035) increased(F= 11.40, q=4.28～8.47, P<0.05) significantly than those of diabetic model group (0.0456 ±0.0057) . The shape and structure of islet cells improved with the up-expressing SOD(t=4.73～4.76, P<0.05)and down-expressing iNOS (t=4.81～5.30, P<0.05) in L.japonica treated group B and C than those in diabetic model group. Conclusion L.japonica might decrease the serum level of FBG through promoting the islet cell recovery by an anti-oxide effect.