To explore the mechanism of DahuangMudan Decoction in the treatment of uterine leiomyoma based on the effect of intestinal flora on reproductive hormones.Methods:A total of 96 patients with uterine leiomyoma admitted to the Second Affiliated Hospital of Hainan Medical College were selected as the research objects and were randomly divided into a control group(n=48)and an observation group(n=48)according to order of visits.The control group was treated with mifepristone and the observation group was treated with DahuangMudan Decoction for 3 months.The changes of reproductive hormone，intestinal flora，cytokines，T lymphocyte subsets，NK cells，Traditional Chinese medicine syndrome score，uterine volume and myoma volume were observed between the 2 groups.Results:1)after treatment，estrogen(E2)，progesterone(P)，follicle stimulating number(FSH)，luteinizing hormone(LH)，interleukin-6(IL-6)，tumor necrosis factor-2 α(TNF-2 α)，CD8+，enterobacteria and yeast-like fungi decreased，while IL-22，CD3+，CD4+，CD4+/CD8+，NK cells，enterococci，bifidobacteria and lactobacillus increased after treatment.The observation group was better than the control group(P<0.05).2)after treatment，the lower abdominal mass，menstrual changes，uterine volume and myoma volume between the 2 groups were significantly lower than those before treatment(P<0.05)，and those in the observation group were significantly lower than those in the control group(P<0.05).3)The clinical effective rate of the observation group was higher than that of the control group(P<0.05).Conclusion:Dahuang Mudan Decoction can inhibit reproductive hormones and increase cellular immune factors by regulating intestinal flora，and to reduce the volume of leiomyoma.