To study the mechanism of contragestational effect of alcohol extract of Verbena officinalis(VO), we observed both the changes of cell morphology, which is observed under phase-contrast microscope and electron microscope or by histochemical study, and the amount of HCG secreted after treatment with VO in 6-8 weeks cultured normal placental tissues in vitro. Our results showed that VO at 25, 50 mg/ml inhibited not only cell growth but also HCG secretion significantly. The histochemical study showed that the amount of HCG secreted and the activity of succinate dehydrogenase (SDH) of trophoblast cells in the VO treated groups were much weaker than that in the control groups. Pathological changes including decreased microvilli, disintegrated cell membrane, enlarged endoplasmic reticula cisternae, myelinlikely changed mitochondria and condensed chromatins arranged below nuclear membrane were also shown in the trophoblast cell in VO treated groups. Conclusively, these data in present study suggested that VO of certain concentrations directly damaged trophoblast cells and inhibited HCG secretion, so they provided some theoretical evidence for the clinical contragestational application of VO.