Nicotinamide (NAM) was evidenced to improve energy metabolism and attenuate oxidative stress during perinatal period. Maternal nutrition programs both short- and long-term development of offspring. This study was aimed to investigate the effect of maternal NAM on milk metabolomics and small intestinal development of kids. Fifteen multiparous does were paired and allocated into 3 treatments: control (C), postpartum (P, supplemented post-kidding), and entire-perinatal (EP, supplemented from d −21 to 28 around kidding). The NAM (5 g/d) was drenched to does at 0700 h. After kidding, the kids were named L_C, L_P, and L_EP, respectively, and fed milk from their mothers until d 28 of life. Individual milk was sampled at 2 consecutive milkings once a week, and blood of kids was sampled on d 14 and 28. At d 28, does and kids were slaughtered to collect tissue samples. The data were analyzed using PROC MIXED of SAS. For kids, the villus height in the duodenum was 24.6% higher in L_P than in L_C, and that in the ileum was 39.7% higher in L_EP than in L_C (P < 0.05). The ratio of villus height to crypt depth of intestine was all increased in L_EP (P < 0.05). The serum IgG tended to increase by maternal NAM (P = 0.078), and the total antioxidant capacity was 56.5% and 62.8% decreased in both L_P and L_EP (P = 0.002). Transcriptome profile of jejunal mucosa showed that glucose and amino acid transporters were improved. The does supplemented with NAM had an improved antioxidative status (P < 0.001), and lower level of milk IL-1β was found in EP (P = 0.033). The MDA of mammary tissue was decreased by NAM (P < 0.05). Moreover, the milk metabolomics profile showed that glycerol was decreased while citramalic acid and sucrose were elevated with NAM supplementation. Metabolism of glycerolipid, galactose, and starch and sucrose were enriched. In conclusion, maternal NAM improved the small intestinal development of kids partially by affecting the milk antioxidative status and metabolites, further suggesting the importance of nutritional strategy from prepartum period and milk feeding in early life for kids.