Abstract: With global warming increasing the frequency of extreme heat events, Acrossocheilus fasciatus aquaculture faces significant challenges. This study examined the effects of feed additive Clostridium butyricum on A. fasciatus under high-temperature stress, aiming to support its cultivation in high-temperature environments. The trial involves four groups with the bacterium added to regular feed at 0, 5×10⁷, 5×10⁸, and 1×10⁹ CFU/g. After 60d feeding, water temperature was increased to 32℃ at a rate of 1℃/24h, and intestinal tissues were collected to analyze digestive enzyme activity, metabolomics, and intestinal microbial diversity. Results showed that C. butyricum-supplemented feed significantly increased weight gain rate and specific growth rate of A. fasciatus while reducing the feed coefficient. Intestinal antioxidant enzyme activities (e.g., hydrogen peroxide and superoxide dismutase) increased significantly, with a concurrent decrease in malondialdehyde content. No significant differences exist in intestinal bacterial composition at phylum level between the two groups, but at the genus level, treatment groups exhibited higher relative abundance of beneficial bacteria, such as Solitrichaceae family, Pseudomonas genus, and Rhodobacter genus, which ensure the intestinal health of A. fasciatus. Key differential metabolites included nucleotides and their derivatives, as well as amino acids and their derivatives. Meanwhile, many fatty acid metabolites changed remarkably. The addition of C. butyricum to feed can enhance fish growth and antioxidant capacity, and help fish cope with heat stress by boosting purine metabolism and modulating gut microbiota.