This paper aims to explore the inhibitory effect of Yueju Pills on breast cancer and decipher the underlying mechanism. A total of 92 SPF-grade SD female rats were involved in this study, and 14 of them were randomly selected into control group. The remaining 78 rats were administrated with 7,12-dimethylbenzanthracene(DMBA) by gavage to establish the breast cancer model. The modeled rats were randomized into model, tamoxifen(1.9 mg·kg~(-1)·d~(-1)), and low-and high-dose(17, 34 g·kg~(-1)·d~(-1)) Yueju Pills groups. The mental state, food intake, and activities of the rats were observed daily, and the body weight was measured on alternate days. After 12 weeks of administration, the rats were sacrificed and the tumor weight was measured. The serum estrogen and progeste-rone levels were determined by enzyme-linked immunosorbent assay. The histopathological changes of the breast and tumor were observed by hematoxylin-eosin staining. Western blot was employed to measure the protein levels of glucose transporter 1(GLUT1), lactate dehydrogenase A(LDHA), phosphofructokinase muscle(PFKM), pyruvate kinase isozyme type M2(PKM2), hexokinase 2(HK2), nuclear factor-kappaB(NF-κB), and phosphorylated NF-κB. The intestinal microbiome was examined by 16S rRNA high-throughput sequencing. The results showed that compared with the model group, high and low-dose Yueju Pills showed the tumor inhibition rate of 15.8% and 64.5%, respectively, and the low dose group had stronger inhibitory effect. Compared with the control group, the model group presented elevated the levels of estrogen and progesterone in serum. The administration of Yueju Pills lowered such ele-vation, and the low-dose group showed stronger lowering effect(P<0.05). Compared with the model group, Yueju Pills reduced the glands with increased breast tissue, the degree of breast duct expansion, the number and area of acinar cavity, the secretions, and the layers of mammary epithelial cells. Furthermore, Yueju Pills down-regulated the expression of GLUT1, LDHA, PFKM, PKM2, HK2, and NF-κB(P<0.05) and altered the diversity, composition, structure, and abundance of intestinal flora. The results showed that Yueju Pills could inhibit breast cancer by regulating the secretion of estrogen and progesterone, glycolysis, inflammatory cytokines, and intestinal flora.