The prohibition of antibiotic growth promoters for animal production has created a demand to explore alternative feed additives to replace antibiotics.Monobutyrate has the potential to replace antibiotics.In this study, we investigated the effects of monobutyrate on broiler growth performance, intestinal development, and caecum microbiota.Total 240 1d-old Arbor Acres broilers were randomly divided into five groups.Each group had eight broilers, and the groups were replicated six times.The broilers were fed a basal diet (CK group), a basal diet containing 0.1% acetyl kitasamycin (Anti group), and basal diets containing 0.15‰, 0.30‰, and 0.45‰ monobutyrate (M1, M2 and M3 group) for 42 days.Compared with the CK group, F/G was significantly decreased in broilers in the M3 group (p <0.05).The relative length and weight of the duodenum were significantly higher in the M1, M2, and M3 groups than those in the CK group.Compared with the CK group, the relative ileum length was significantly increased in the M2 and M3 groups (p <0.05).Compared with those of the CK and Anti groups, Rikenellaceae, Alistipes, Sellimonas, and Ruminococcus_2 were enriched in the M3 group (p < 0.05).The results of this study indicated that monobutyrate promotes broiler growth performance, improves intestinal development, and regulates microbiota composition