Objective To investigate the effects of aqueous extract from Desmodium styracifolium (Osb.) Merr.(Ds) on oxidative stress of renal calcium oxalate (CaOx) rat models.Methods The models of renal CaOx were established with ethylene glycol in drinking water and ammonium chloride by gavage.The 50 adult healthy male Wistar strain rats were randomly divided into 5 groups (10 of each),i.e.,normal control group (group A),calcium oxalate model group (group B),low-dose Ds extract-treated group (group C),moderate-dose Ds extract-treated group (group D) and high-dose Ds extract-treated group (group E).Group A was established with drinking water and physiological saline by gavage (2 ml per day),group B was established with 1％ ethylene glycol in drinking water and 2％ ammonium chloride by gavage (2 ml per day),group C,D and E were established with aqueous extract from Ds (0.6,1.2 and 2.4 g/ml,respectively) by gavage on the basis of group B (2 ml per day).After feeding for 28 days,blood and renal samples were collected.The presence of CaOx crystals was scored in left kidneys under hematoxylin and eosin staining,and the levels of malondialdehyde (MDA),superoxide dismutase (SOD),glutathione peroxidase (GSH-Px) and catalase (CAT) in the blood and right kidney homogenate were measured as indicators of oxidative stress.Results For the formation of CaOx crystals,the scores of group B were significantly higher than group A (P＜0.01),the scores of group C,D and E were significantly lower than group B (P＜0.01),especially the group D showed the best effect.For the parameters of oxidative stress,compared with group A,the concentration of MDA in blood and kidney tissues of group B significantly increased (P＜0.01),which significantly decreased (P＜0.01) after the intervention of Ds (group C,D and E).Compared with group A,the content of SOD,CAT and GSH-Px in group B significantly decreased (P＜0.01),the SOD level in renal homogenate significantly increased (P＜0.01) after the intervention of Ds (group C,D and E).In group D,the SOD and GSH-Px levels in blood significantly increased (P＜0.05).But the Ds showed no significant influence either for CAT in blood or GSH-Px and CAT in renal homogenate (P＞0.05).Conclusion The moderate-dose Ds extract seems to prevent the formation of renal CaOx in rats,which is probably due to its antioxidant effects.