Abstract: It is observed through clinical studies that Ilexonin A is highly effective in the treatment of throm-botic diseases.Pharmacological experiments indicate that llexonin A can reduce the size of the throm-bus. Now it is belieyed that a balan-ce between Thromboxane A₂（TXA₂） and prostacyclin （PGI₂） is impor-tant in the formation of thrombus. In order to study the anti-throm-bosis mechanism of llexonin A, this paper mainly studies how lle-xonin A affects the artery of rats to produce Prostacyclin-like subs-tances. It is demostrated that Ilexonin A promotes artery to produce Pros-tacyclin-like substances both in vivo and vitro,which may be resul-ted from one of its anti-throm-bosis mechanisms of action.