Objective:To explore the abortion effect and mechanism induced by Chinese herbal medicine rhubarb extract.Methods:The pregnant mice at day 3 of gestation were Drenched by Aqueous extract of rhubarb at different doses (7,5,2.5 g/kg)once per day for five days,and mices in control group were oral administration of same volume of saline.All mices at 12 day of gestation were sacrificed.estradiol and progesterone levels in serum were detected by Radioimmunoassay;Content of IFN-γ, IL-2 and TNF-αin uterine lysates were measured by ELISA, macrophages in endometrium were determined by immunohistochemical method, mast cells in endometrium were tested by Toluidine blue staining, respectively.Results: showed as follows:With increasing dose of rhubarb extract,abortion rate and resorption rate were gradually increased and was 100%abortion in 7g/kg treatment groups.Estrogen and progesterone content showed a downward trend,IFN-γ,IL-2 and TNF-αin uterine lysates and the numbers of macrophages and mast cells were significantly higher in mices Drenched by Aqueous extract of rhubarb than in the control.Conclusion: These results show that rhubarb extract not only interfere stability of pregnancy state in pregnant mices because of its diarrhea,but also can directly affect endometrial environment in early embryonic mice,Resulting in abortion.