[Objective] To investigate the effects of Weizmannia coagulans BC-G44 on the intestinal microbiota structure, barrier function, and inflammatory response in the colon of the rat model of antibiotic-associated diarrhea (AAD). [Methods] A total of 30 five-week-old Sprague-Dawley (SD) rats with similar body weights were randomized into five groups (n=6): control (Con), model (Mod), low-dose W. coagulans BC-G44 (LBC-G44), medium-dose W. coagulans BC-G44 (MBC-G44), and high-dose W. coagulans BC-G44 (HBC-G44). The experiment encompassed a modeling period (7 days) and a recovery period (12 days). During the modeling period, rats in the Con group were administrated with normal saline at 2 mL/d by gavage, while those in the Mod, LBC-G44, MBC-G44, and HBC-G44 groups were administrated with a mixture containing clindamycin, ampicillin, and streptomycin (2 mL/d) by gavage to induce AAD. During the recovery period, the Con and Mod groups continued to receive normal saline, while the LBC-G44, MBC-G44, and HBC-G44 groups received W. coagulans BC-G44 suspensions at 10⁷, 10⁸, and 10⁹ CFU/d, respectively. On day 19, colonic tissue samples were collected for histological examination, and the concentrations of cytokines, and the expression levels of barrier proteins and inflammation-related genes in the colonic mucosa were measured. Furthermore, the microbiota composition and metabolites in the colonic chyme were analyzed. [Results] On day 7 of modeling, rats in the Mod, LBC-G44, MBC-G44, and HBC-G44 groups exhibited diarrhea, weight losses, and reduced food intake compared with those in the Con group (P<0.05). On day 19, compared with the Mod group, the MBC-G44 and HBC-G44 groups showed increases in the colonic mucosa thickness and goblet cell number (P<0.05). The HBC-G44 group showed increased relative abundance of Bacteroides and concentrations of lactate in the colonic chyme (P<0.05), elevated levels of d-lactic acid (d-LA) and diamine oxidase (DAO) in the colonic mucosa, and up-regulated relative mRNA levels of Claudin-1, Occludin, and MUC2 in the colonic mucosa (P<0.05). Meanwhile, compared with the Mod group, the MBC-G44 and HBC-G44 groups showed down-regulated relative mRNA levels of Toll-like receptor 4 gene (TLR4) and nuclear factor-kappa B gene (NF-κB) (P<0.05), and reduced concentrations of tumor necrosis factor (TNF)-α and interleukin (IL)-1β (P<0.05) in the colonic mucosa. [Conclusion] W. coagulans BC-G44 can ameliorate antibiotic-induced colonic injury, regulate the colonic microbiota composition and metabolites, enhance intestinal barrier function, and reduce intestinal inflammatory responses in rats, thus alleviating the symptoms of AAD.