To observe the effect of fresh Radix Rehmanniae Recens on JAK2/STAT3 pathway in acute-on-chronic liver failure rats.Methods:Thirty male Wistar rats were randomly divided into control group and experimental group according to 1:4 ratio.Rats in experimental group were firstly induced to hepatic fibrosis model with carbon tetrachloride，and then randomly divided into model group and treatment group according to the ratio of 1:1.Acute attacks were performed with D-galactosamine and a rat model of chronic acute liver failure was established.The treatment group was given intragastrically with the fresh Radix Rehmanniae Recens 7 days before the acute attack.Rats in each group were harvested 24 hours after acute challenge.Serum endotoxin，interleukin-6 levels，and expression of JAK2 mRNA and STAT3 mRNA in liver tissue were measured.Results:The expression of JAK2 mRNA and STAT3 mRNA in the liver tissue of the model group was lower than that in the control group and the model group.The difference was statistically significant (P<0.05).There was no significant difference in the expression of JAK2 mRNA and STAT3 mRNA between the treatment group and the control group (P>0.05).The serum endotoxin level in the model group was obviously higher than that in the control group and the treatment group，and the difference was statistically significant (P<0.01).There was no significant difference in serum endotoxin expression between the treatment group and the control group (P>0.05).Serum interleukin-6 levels in the model group were higher than those in the control group and the treatment group，but the difference was not statistically significant (P>0.05).Conclusion:Fresh Radix Rehmanniae Recens can reduce the absorption of toxins in the intestine and promote the activation of JAK2/STAT3 pathway，but the mediator may not be IL6，and the relevant mechanisms need to be further improved.