Objective To detect expression of connective tissue growth factor (CTGF) and nuclear factor-κB (NF-κB)p65 in renal tissues，and investigate the mechanism of Norcantharidin (NCTD) on renal interstitial fibrosis prevention. Methods uninephrectomized SD rats were received intraperitoneally injections of bovine serum albumin (BSA). The nephropathy rats were randomly divided into model group (BSA group, intraperitoneally injections of BSA 5g·kg-1·d-1) and NCTD group (intraperitoneally injections of BSA 5g·kg-1·d-1and NCTD 0.1mg·kg-1·d-1). An additional set of uninephrectomized rats were only given saline as control group. At week 9, the rats were sacrificed and the remnant kidney was collected. Renal pathological change was observed by light microscopy and electron microscopy. Expression of CTGF mRNA and NF-κBp65 mRNA in renal tissue was semi-quantitative analyzed by RT-PCR. CTGF protein expression was detected by western blot. NF-κBp65 protein expression was detected by immunohistochemistry. Result ⑴By light microscope, in BSA group it was showed that glomerular sclerosis existed and lots of inflammatory cell infiltrated in renal interstitium with segmental interstitial fibrosis. By electron microscope, obvious electron dense deposits existed and foot process fusion was seen extensively in BSA group. After intervention of NCTD, tubulointerstitial lesion（TIL）score significantly decreaded (P＜0.05). ⑵Compared with BSA group, expression of CTGF mRNA and NF-κBp65 mRNA in NCTD group were down-regulated (P＜0.01). ⑶Compared with BSA group, protein expressions of CTGF in NCTD was down-regulated (P＜0.05) by western blot. ⑷Compared with BSA group, deposited area and positive cell population of NF-κBp65 decreased (P＜0.05). Conclusion NCTD could effectively prevent renal tubulointerstitial fibrosis by significantly down-regulating expressions of CTGF and NF-κBp65.