The purpose of this study was to investigate the effects of adding Pennisetum purpureum (P. purpureum, also known as Napier grass or elephant grass) to the diets of late gestation on the antioxidant indexes, immune indexes and faecal microbiota of sows. At the 90 days of gestation, 300 healthy sows were randomly divided into three groups, and they received the basic commercial diet or added 5% P. purpureum and 10% P. purpureum, respectively. The experiment started from 90 days of gestation to parturition. The results showed that the total antioxidant capacity, immunoglobulins and serum equol concentrations of sows on 100 days of gestation and at parturition increased linearly (p < .05) with the increase of the content of P. purpureum in the gestation diet. The 5% P. purpureum increased the relative abundance of Bacteroidetes (p = .027) and Actinobacteria (p < .001) at phylum level, Coriobacteriaceae (p < .001) at family level and Prevotellaceae_UCG_001 (p = .004) at genus level, and decreased the relative abundance of Escherichia_Shigella (p < .001) at genus level. In summary, this study shows that the additive of P. purpureum can increase the concentration of serum equol, improve the antioxidant capacity and immune function of sow in late gestation. In addition, the additive of 5% P. purpureum in the diet might change the composition of intestinal microbiota of sows, particularly the relative abundance of Coriobacteriaceae (p < .001) increased.