Abstract: Objective To observe the influence of oral administration of ciprofloxacin on hepatic TLR4 signaling activated by metabolic endotoxemia in rats with nonalcoholic steatohepatitis （NASH） induced by high-fat diet. Methods Thirty male SD rats were divided randomly into model and intervention group fed with high-fat diet and normal group fed with normal diet. Rats in intervention group were administrated with oral ciprofloxacin from 9th week. At the end of 12th week,the endotoxin level in portal vein,fasting blood glucose and serum lipid were detected. NAS score was evaluated. The protein and mRNA levels of hepatic TLR4 and IRS-1 were detected by real time PCR or Western bloting. Liver and serum pro-inflammatory cytokines levels were tested by ELISA. Results Serum endotoxin level in model group was significantly higher than that in normal group（0.361±0.018 EU/ml νs. 0.324±0.013 EU/ml,P<0.01）;NAS score in ciprofloxacin-intervened group declined（4.40 ±0.26 vs. 6.9±0.3 in model,P<0.05）;TLR4 mRNA levels and its protein expression in model groups were 8.7 times and 1.4 times higher than that in normal group,and declined by 51% and 14% in intervention group;Compared with the normal group,IRS-1 mRNA and its protein expressions in model group declined by 69% and 47%,and increased 2.3 times and 1.6 times in intervention group;Serum and hepatic TNF-ɑ and IL-6 levels in model rats increased significantly （P<0.05）,which decreased in intervention groups. Conclusion Metabolic endotoxemia activates TLR4 signaling in liver and might play a role in the onset of NASH. Oral ciprofloxacin administration could reduce gut-derived endotoxin.