Objective To explore the application value of right heart contrast echocardiography in patients with transient ischemic stroke (TIA) of unknow cause.Methods Totally 120 patients with TIA (TIA group) and 60 cases of normal healthy volunteers (normal group) were enrolled.Two groups underwent right heart contrast echocardiography to observe whether there was a foramen ovale arteriosus (PFO) or not.Diagnostic criteria were left ventricular internal appearing micro bubble≥5 that came from the right atrium to left atrium in three cardiac cycles.Results Small and medium amount of right to left shunt had no significant difference between TIA group and normal group (both P＞0.05),and large amount of right to left shunt had significant difference between the two groups (P＜0.01).Conclusion Contrast echocardiography can effectively diagnose of PFO,and amount of right to left shunt of PFO has relationship with the onset of TIA.