Abstract: Objective To explore the significance of nuclear factor kappa B(NF-κB)related gene in the pathogenesis of the rats' kidney with chronic fluorosis. Methods Kidney cell apoptosis was detected with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling(TUNEL)and flow cytometry.Immunohistochemistry and real-time fluorescence quantitative PCR(RT-PCR)were used to detect the expressions of p50,p65,IκBαand Bcl-2,Bax protein and mRNA. Results The positive expressions of p50 and p65 in turbular epithelial cells were 134.65±9.71,113.62±10.49, 105.30±8.00 and 119.74±5.17,111.90±6.90,101.71±9.31 for the rats in control,low fluorine,and high fluorine group,and the numbers of positive nuclear were decreased with the fluorine concerntration,but the expressions of IκBαwere increased(152.67±3.36,155.75±3.37,156.29±3.78),wtih significant differences.Compared with the control group,the expression of Bcl-2 was decreased and Bax's was increased(P<0.05).The expressions of all the indicatos'mRNA in the kidney were the same as those of the protein.The apoptosis cells were increased with the fluorine concentration(P<0.05). There were correlations between p50,p65,IκBα and the ratio of Bcl-2/Bax(r=0.696,r=0.720,r=-0.435,P<0.05). Conclusion The apoptosis of nephridial tubule epithelial cells caused by the reduction of NF-κB related gene is one of the pathogenesis in the kidney injury of chronic fluorosis in rats.