Objective　To explore the characteristics of T wave alternans (TWA) in aortic stenosis (AS) in school-aged children. Methods TWA was analyzed in 15 AS patients and 60 age-matched normal children using Microvolt T-Wave Alternans and the incidence of sustained TWA was compared between two groups. Myocardial ischemia during treadmill test was studied in sustained TWA and non-sustained TWA in AS patients. Results Compared with normal children, the incidence of sustained TWA was significantly increased in AS group (P<0.01). In AS school-aged patients, the incidence of myocardial ischemia is higher in sustained TWA than in non-sustained TWA during treadmill test (P<0.05). Conclusions AS school-aged children have electrophysiologic basis for sunstained TWA. TWA is closely related to myocardial ischemia during treadmill test. Sustained TWA could be used as an important electrophysiologic index to assess the cardiac function in children with AS.