The present study aims to investigate the effect of dietary supplementation with Lactobacillus plantarum on intestinal flora, plasma metabolites, and meat quality in the Sunite sheep. Three-month-old Sunite sheep (12 sheep) with good health and the same genetic background were selected as the test objects, and then randomly divided into two groups: The control group was fed a basal diet (C group, a typical corn-soybean diet) without any antibiotics, drugs, or growth promoters, and the Lactobacillus plantarum group was supplemented with Lactobacillus plantarum at 3×1010 cfu/g using the diet of the control group (R group, a typical corn-soybean diet, the number of viable bacteria was 3×1010cfu/g Lactobacillus plantarum), where the feeding period lasted for 90 days. After slaughtering, the intestinal contents and the longissimus dorsi muscle were determined using high-throughput sequencing technology, and liquid-chromatography metabolomics, in order to analyze the gut microbiota, plasma metabolites, and meat quality of Sunite sheep. The results showed that the feeding Lactobacillus plantarum significantly increased the abundance of Bacteroidetes, Verrucomicrobia, Bacteroides, Christensenellaceae_R-7_group, Rikenbacteriaceae_RC9_gut_group, Ruminococcaceae_UCG-010, and Ruminococcaceae_UCG-005 (P<0.05), whereas, significantly decreased the abundance of Firmicutes, Proteobacteria, Alistipes, and Prevotellaceae_UCG-003 (P<0.05). The plasma metabolite results showed that the Lactobacillus plantarum significantly increased the content of Indole-3-propionic acid, Cortisol, Glycocholic acid, L-arginine and Ramipril (P<0.05), but decreased the content of 3-hydroxylauric acid (P<0.05). A correlation analysis showed that the Bacteroidetes and Prevotellaceae_UCG-001 were significantly positively correlated with the plasma metabolite Glycocholic acid (P<0.05). In addition, the Lactobacillus plantarum had significantly improved the values of meat brightness (L*), the yellowness (b*), and the pH24h (P<0.05), but reduced the meat cooking loss, and the shear force (lower cooking loss and shear force values for better tenderness) (P<0.05). Consequently, the addition of Lactobacillus plantarum to the diet can be widely expected to ameliorate the quality of meat via changing the composition and structure of the intestinal flora in the Sunite sheep. The gut bacteria was used to regulate the participation of plasma metabolites in the metabolism of body fat, thus affecting cholesterol, bile acid secretion, and synthesis pathway. The finding can provide a theoretical reference to determine the relationship between intestinal flora and plasma metabolites by feeding probiotics, there by tailoring the lipid metabolism pathway of ruminants for the better quality of Mongolian sheep.