Objective To observe the change of the precentral gyrus bloodbrain barrier ultrastructure in the epilepsy rats induced by coriaria lacton and affected by topimmate, and to study the effect of the bloodbrain barrier on the mechanism of the falling sickness and therapy by topimmate. Method Thirty healthy male Sprague Dawley rats were randomly divided to three groups: the control group, the epilepsy group and the treatment group. The coriaria lacton was injected into the lateral ventricles of the rats in the epilepsy and treatment groups, and the epilepsy animal model was established. Gastric perfusion was performed 1 hour after falling epilepsy to the rats of the treatment group and was repeated one time per day for 7 days. The precentral gyrus was cut 7days later, and the ultrathin sections were made. The change of blood brain barrier ultrastructure was observed under electron microscope. Results The endothelium, basement membrane, pericyte of epilepsy group displayed obvious edema. The electron density reduced, and the edema of the treatment group alleviated. There was signifcant difference between the epilepsy group and the control group（P<0.05）,in the thinkness of endothelium cytoplast, basement membrane and pericytes cytoplast of bloodbrain barrier. So was the case between the treatment group and the epilepsy group（P<0.05）. Conclusion 1.Endothelium, basement membrane and pericytes of bloodbrain barrier of the epilepsy rats induced by coriaria lacton displayed obvious edema, and topimmate weakened th