Objective To investigate the effect of probiotics intervention on rats with acute-on-chronic liver failure ( ACLF) and related mechanism. Methods A total of 44 male Sprague-Dawley rats were randomly divided into six groups using a random number table, i. e., control group 1 ( C1 group with 6 rats without any intervention) , model group 1 ( M1 group with 8 rats treated with intraperitoneally injected40% CCl4 oil solution for 10 weeks, followed by phosphate-buffered saline by gavage since week 7 and D-galactosamine acute attack at the end of week 10) , probiotics intervention group 1 ( Y1 group with 8 rats treated with the same modeling method as the M1 group, and probiotics solution was given by gavage) , control group 2 ( C2 group with 6 rats without any intervention) , model group 2 ( M2 group with 8 rats treated with intraperitoneally injected 40% CCl4 oil solution, followed by D-galactosamine acute attack at the end of week 10 and phosphate-buffered saline by gavage at 48 hours after attack, and they were sacrificed at the end of week 12) , and probiotics intervention group 2 ( Y2 group with 8 rats treated with the same modeling method as the M2 group, and probiotics solution was given by gavage) . Body weight, liver function, and liver histopathology were observed before and after intervention. ELISA was used to measure the levels of endotoxin and endocrine immunoglobulin A ( s IgA) in plasma, Western Blot was used to measure the content of the intestinal tight junction protein Occludin, RT-PCR was used to measure the mRNA expression of Occludin and ZO-1, and a selective medium was used to measure the changes in related indices including intestinal flora. A one-way analysis of variance was used for comparison of continuous data between multiple groups, and the SNK-q test was used for further comparison between two groups. Results There were significant differences in body weight, liver index, alanine aminotransferase, aspartate aminotransferase, total bilirubin, plasma endotoxin, s IgA, and mRNA expression of Occludin and ZO-1 between the C1, M1, and Y1 groups ( F = 27. 65, 8. 96, 61. 37, 18. 27, 21. 00, 87. 01, 67. 10, 101. 50, and105. 40, all P < 0. 05) , as well as between the C2, M2, and Y2 groups ( F = 14. 04, 12. 85, 14. 02, 11. 39, 35. 80, 19. 14, 15. 37, 25. 02, and 126. 00, all P < 0. 05) . There was no significant difference in the protein expression of Occludin between the C1, M1, and Y1 groups ( F = 16. 40, P < 0. 05) . There were significant differences in the content of Lactobacillus, Bifidobacterium, Enterococcus, and Enterobacter between the C1, M1, and Y1 groups ( F = 77. 95, 66. 61, 25. 63, and 33. 29, all P < 0. 05) , as well as between the C2, M2, and Y2 groups ( F = 21. 50, 22. 62, 6. 71, and 17. 74, all P < 0. 05) . Conclusion Intestinal flora disturbance and intestinal barrier dysfunction are observed in rats with ACLF, and probiotics intervention can remodel the structure of intestinal flora, maintain intestinal barrier function, and promote liver repair.