Abstract: AIMTo study the effect of 3,4-oxo-isopropylidene-shikimic acid (ISA) against arteriovenous shunt and middle cerebral artery thrombosis (MCAT) in rats. METHODSArteriovenous shunt model was adopted to measure thrombus weight; The neurologic deficit (ND) and the infarct size (IS) of the middle cerebral thrombosis (MCAT) model induced by FeCl₃ were observed; The effect of ISA on platelet aggregation rate of rat and rabbit by giving ISA in vivo and in vitro was studied. RESULTSISA 25, 50, 100 and 200 mg·kg^-1 ig was shown to reduced the weight of thrombus in arteriovenous shunt model; ISA 50, 100 and 200 mg·kg^-1 ig for 2 times in 24 hours, attenuated the ND of rats subjected to MCAT; ISA 100 and 200 mg·kg^-1 reduced IS of rats after MCAT by 27.8% and 31.6%, respectively; ISA 50, 100 and 200 mg·kg^-1 ig inhibited platelet aggregation of normal rats; ISA 10^-3～10^-5 mol·L^-1, inhibited rabbit platelet aggregation in vitro. CONCLUSIONISA inhibited thrombosis by anti-platelet-aggregation.