Objective The aim of this study was to establish a reasonable protocol for a rat model of ferric chloride-induced carotid arterial thrombosis by ultrasonic continuous evaluation.Methods Twenty SD rats were randomly divided into four groups and then treated with 20％,30％,40％ or 50％ concentrations of FeCl3,respectively.The vascular conditions were evaluated by 14L ultrasonic probe,at 10 mins,15 mins,and 20 mins.We then selected the best group through the examination of the rate of spontaneous reperfusion of blood vessels and the rate of reperfusion after intravenous injection of urokinase.At the end of the experiment,vessels were fixed in 10％ formalin solution and stained with HE.Results After external application of FeCl3 on rat common carotid artery for 20 mins,the artery occlusion rate was 100％,20％,0％ and 0％ in animals receiving 50％,40％,30％ and 20％ FeCl3,respectively.After external application of FeCl3 on rat common carotid artery for 120 mins,the spontaneous revascularization rate was 0％ in 50％ concentration group whereas were 100％ in rest other groups (P＜ 0.001).In 50％ concentration group,the partial recanalization rate was 40％ after intravenous injection of urokinase.HE staining revealed that the thrombus was dense and the lumen was partially recanalized after the urokinase intervention in 50％ concentration group.Conclusion By use of uultrasonic continuous evaluation of ferric chloride-induced thrombosis of rat common carotid artery,we have demonstrated that external application of 50％ ferric chloride solution for 20 mins is effective for the formation of thrombus model,which may be suitable for the studv of thrombolysis.