Objective To investigate the protective effect and mechanism of Klotho protein on oxidative stress in renal tubular epithelial cells of experimental rat nodels of renal calcium oxalate stone.Methods The 30 SD rats,6-8 weeks old,were randomly divided into 3 groups (10 of each),normal control group(group A),calcium oxalate model group(group B),drug plus calcium oxalate model group (group C).Group A was established with physiological saline by garage each day,group B was established with 1％ ethylene glycol in drinking water + 2％ ammonium chloride by garage (2 ml/d),group C was established with Fosinopril 2.5mg + Valsartan 15mg aqueous solution 2 ml by gavage on the basis of group B (2 ml/d).4 weeks later,the level of malondialdehyde (MDA),superoxide dismutase (SOD),catalase (CAT) and glutathione peroxidase (GSH) in the kidney homogenate were measured by double antibody sandwich enzyme-linked immunosorbent assay (ELISA),Polymerase chain reaction (RT-PCR) was used to measure expression of Klotho and Nrf2 mRNA,and Western Blot was used to measure the expression of Klotho and Nrf2 protein.Results The level of MDA in group B [(12.43 ± 0.43) μmol/mg] was significantly increased compared to group A[(8.67 ±0.84) μmol/mg,P ＜0.05] and group C [(7.97 ±0.81) μmol/mg,P＜0.05],while group A was close to group C (P ＞0.05).In group A,B,and C,the levels of SOD were (247.89 ± 2.45),(109.54 ± 4.21),and (189.74 ± 10.47) U/mg,respectively;the levels of GSH were (38.98 ± 4.55),(26.87 ± 3.92),and (31.29± 2.54) μmol/mg,respectively;CAT were (138.47 ± 8.74),(119.87 ± 8.45),and (127.46 ± 7.45) U/mg,respectively.The levels of SOD,GSH,CAT in group B were significantly lower than that in group A and C,while those in group B were close to group A (P ＞ 0.05).The expression of Klotho and Nrf2 mRNA in group B [(0.208 ± 0.036) and (0.499 ± 0.086)] were significantly lower than group A (1.011 ± 0.174 and 1.023 ± 0.139,P ＜ 0.05)and group C(1.123 ±0.248 and 1.023 ±0.139,P ＜0.05).The expression of Klotho and Nrf2 protien were also significantly lower than that in group A and C (P ＜0.05).Conclusions Valsartan and Fosinopril could prevent the formation of renal CaOx stones by upregulating expression of low level Klotho gene induced by ethylene glycol.This effect may be involved with activation of Keapl-Nrf2-ARE signaling pathway.