The strong connection between undernutrition and gut microbiota (GM) has enabled microbiota-targeting to become an evolving strategy, which witnessed urgent need for fortified formula of supplementary food in undernutrition therapy. Using undernourished pigs as models, we investigated how corn- and millet-based nutritional supplement acted differently in modulating microbiota. Undernourished pigs at age of 9 weeks were fed with pure maize diet (Maize), corn-based (CSB+) and millet-based (MSB+) supplementary food for 3 weeks. Compared with Maize group, both CSB+ and MSB+ improved serum total protein and globulin level, but no physiological improvement was observed by short-term food intervention. MSB+ shown superior influence on GM immaturity which were more normally-grown like at both structural and functional level. Higher level of Bacteriodetes, Firmicutes and lower level of Preteobacteria were detected in MSB+ fed piglets in contrast with CSB+. Lachnospira.spp was significantly raised after nutritional intervention, indicating high correlation with the undernutrition-associated phenotype. Thus, especially from the GM aspect, millet could be one promising source to help undernourished children reconstruct balanced microbiota in short therapeutic term.