[Objectives] To investigate the effects of early fructo-oligosaccharide (FOS) intervention on the antioxidant capacity, colonic barrier function, and colonic microbiota and metabolites in suckling piglets. [Methods] A total of six litters (10 piglets per litter) of Duroc×Landrace×Yorkshire newborn piglets were selected. Within-litter grouping was adopted with equal average body weight per group: five piglets from each litter were assigned to the control group (CON), and the other five formed the experimental group (Fos). From the second day after birth, the Fos group received daily oral administration of a FOS solution at an effective dose of 3 g/d per piglet, while the control group received an equal volume of normal saline. The trial lasted for 21 days. [Results] Early FOS intervention reduced the total cholesterol level and increased the concentrations of urea nitrogen, total protein, and albumin in the serum samples of suckling piglets (P<0.05). Early FOS intervention enhanced the total antioxidant capacity and glutathione peroxidase activity (P<0.05), while reducing the malondialdehyde content (P<0.05) in the serum. In addition, it enhanced the catalase activity and decreased the malondialdehyde content in the colonic mucosa (P<0.05). Early FOS intervention decreased the diamine oxidase (DAO) level in the serum (P<0.05), increased the DAO and D-lactic acid levels in the colonic mucosa (P<0.05), and up-regulated the expression of colonic barrier function-related genes (Claudin-1, ZO-1, Occludin, MUC1, MUC2, and MUC4) (P<0.05). Early FOS intervention improved the alpha diversity indexes of colonic bacteria (P<0.05) and induced separation of microbiota in colonic chyme of 14- and 21-day-old piglets (P<0.05). It altered the composition of colonic chyme microbiota at both phylum and genus levels (P<0.05). Furthermore, early FOS intervention increased the concentrations of lactic acid and short-chain fatty acids in the colon of suckling piglets (P<0.05). [Conclusions] Early FOS intervention enhances the antioxidant capacity, upregulates the mRNA levels of colonic barrier function-related genes, modulates the colonic microbiota, and promotes the production of lactic acid and short-chain fatty acids in suckling piglets.