This study was conducted to evaluate the effects of green forage on the onset of puberty and estrus cycle, the development of reproductive organ and diversity of the gut microbiota in Meishan prepubertal gilts.Twenty purebred prepubertal Meishan gilts (ages 93.3 ±-6.8 d;initial body weight 25.3 ± 0.8 kg)were randomly allocated to one of two groups with 10 repeats for each group: control (CON) and Green Forage group (GF).The control basal diets were formulated to meet or exceed Chinese Feeding Standard of Swine (2004).In Green Forage group we used Chinese cabbage instead of part of basal diet with almost iso-energetic and iso-protein.The control group gilts fed 1.08kg, 1.30kg, 1.64kg of basal diets (corn-soybean meal diets) per day at stage 1 (20-30kg), stage 2 (30-40kg) and stage 3 (40kg to the fourth estrus), respectively.The Green Forage group gilts were fed 1.2kg, 1.8kg, 2.4kg of Chinese cabbage, and 1.02kg, 1.21kg, 1.54kg of basal diets at stage 1 (20-30kg), stage 2 (30-40kg) and stage 3 (40kg to the fourth estrus), respectively.The age at first estrus of gilts fed green forage was delayed compared with the control gilts (152.4 d vs 135.2 d, P =0.003).The number of large follicles (>5mm) were increased compared with the control gilts (16.4 vs 12.6, P =0.041).The concentration ofIGF-1 in follicular fluid was increased significantly compared with the control gilts.There was no effect of green forage on estrus cycle and duration of estrous.The gilts fed green forage had higher levels of intestinal microbial richness and biodiversity than the control gilts.This study demonstrates that the green forage can promote the development of reproductive organ in Meishan prepubertal gilts.Meanwhile, this may be a hint that the improvement of the reproductive organs may be associated with the change of intestinal microorganism.