Objective To investigate the miscarriage prevention effect and mechanism of Taxilli Herba decoction on threatened abortion in rats. Methods After co-housing 72 SPF-grade SD rats with a male-to-female ratio of 2:1, 48 pregnant rats were divided into a normal group, a threatened abortion model group, a positive control group, as well as high, medium and low-dose groups of Taxilli Herba decoction, with 8 rats in each group. The positive control group was given intragastric administration of 3.02 mg/kg dydrogesterone. The low-dose, medium-dose and high-dose groups of Taxilli Herba decoction were given intragastric administration of 2.5 g/kg, 5 g/kg and 10 g/kg respectively. The normal group and thmal saline once a day for 10 consecutive e model group were given intragastric administration of an equal volume of nordays. On the 10th day, after intragastric administration of the corresponding liquid medicine, except for the normal group, the remaining groups were additionally given intragastric administration of 3.75 mg/kg mifepristone suspension. Subsequently, the effects of Taxilli Herba on the vaginal bleeding rate, abortion rate, etc. were observed.Determination of follicle-stimulating hormone(FSH),luteinising hormone(LH),estrogen(E),progesterone(P),vascular endothelial growth factor(VEGF),testosterone(T),aromatase in serum and E,P in ovary of pregnant rats by ELISA.The positive expressions of estrogen receptor(ER),progesterone receptor(PR),vascular endothelial growth factor receptor 2(VEGFR2) and platelet endothelial cell adhesion molecule-1(CD31) in uterine decidua of pregnant rats were observed by immunofluorescence staining, and semi-quantitative analysis was performed. Results After the establishment of mifepristone, the vaginal bleeding rate and abortion rate of pregnant rats increased significantly. The treatment group was able to effectively reduce the vaginal bleeding rate and abortion rate of pregnant rats. Taxilli Herba water decoction could increase the contents of serum E,P,VEGF and ovary E,P(P<0.05),decrease the content of serum LH and maintain the secretion of FSH, enhance the expression activity of ER,PR,VEGFR2 and CD31 in decidual tissue. Conclusion Taxilli Herba has obvious miscarriage prevention effect on threatened abortion model rats. The mechanism of action is related to regulating the normal physiological function of hypothalamic-pi-tuitary-goned axis(HPG) upstream of uterus, enhance the expression activity of downstream “P/PR/VEGF/VEGFR2” and “E/ER/VEGF/VEGFR2” pathways.