Abstract: Healthy, uniformly sized juvenile Megalobrama amblycephala initial average weight (5.12±0.05) g “Hua Hai No. 1” were used for the experiment to investigate the effects of early feeding Lactobacillus plantarum (LP FF34) on phasic changes in the intestinal microbiota and its influence on high glucose metabolism in juvenile. From 0w to 6w, they were uniformly fed with LP FF34 experimental diet (commercial feed + 10⁸ CFU/g LP FF34). From 7w to 12w, they were uniformly fed with high glucose diet (HW). Plasma, liver, intestine and intestinal contents were collected at 0w, 2w, 4w, 6w, 8w, 10w and 12w. At 4w, the levels of glutathione (GSH) and the activities of catalase (CAT) and total superoxide dismutase (T-SOD) in the liver were significantly higher than those at 2w and 6w. In contrast, the malondialdehyde (MDA) levels were the opposite (P<0.05). Intestinal microbiota indicated that at 6w, the relative abundance of Firmicutes and Desulfobacterota and the ratio of Firmicutes to Bacteroidetes were significantly decreased (P<0.05). At 4w and 6w, the relative abundance of Burkholderiales significantly increased compared with 0w and 2w (P<0.05). As the duration of LP FF34 supplementation increased, the contents of metabolites associated with anti-inflammatory and methylation processes (docosahexaenoic acid, S-adenosylmethionine and 5-methylcytosine) in the intestine significantly increased (P<0.05). At 12w, the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and glucose (GLU-HK) in the plasma were significantly lower than those at 8w (P<0.05). Feeding LP FF34 diet to juvenile M. amblycephala could affect the structure of the intestinal microbiota, increase the anti-inflammatory and antioxidant capacity of intestinal tissue, improve DNA methylation metabolite levels, thereby preventively improving the metabolic utilization of high carbohydrate diets in M. amblycephala during the later stages of cultivation. This paper provides a theoretical basis for the effect of probiotics on intestinal function and nutritional metabolism.