Abstract: To investigate the placental pathological changes after treatment of replenishing kidney formula,early abortion rat model was established by Bromocriptine at 6-8 gestation day,the model rats were treated with high and low dosage of the herbs and the progesterone as the positive control, the rats were sacrificed at 12 gestation day and the ultrastructure of the placenta were observed by electron microscope.The results find that compared with the normal control the basement membrane of thetrophoblastic epithelium of model group was thickened and tortuous, within the basement membrane there were lots of dense microspherical particles, mitochondrial showed coagulating and vacant, the cisternae of the rough endoplasmic reticulum（rER） were dilated and contained flocky material and also the degranulation of ribosomes on the rER were frequently found, the capillary endothelium was thicked with microvilli-like projections. In herbs and progesterone groups, smooth endoplasmic reticulum（sER） increased and dilated, there were plenty of mitochondria and some lipid droplet in cytoplasm, organell were normal mainly. The results suggested that the Bromocriptine could induce changes of placental structure and influenced placental normal function. Kidney replenishing herbs could reverse morphological alteration of ultrastrcture in abortion placenta,and converted to benefit in hormone synthesis, finally achieved the aim to prevent abortion.