Objectives　To assess the cardiovascular function in obese children. Methods　A total of 30 obese children and 50 age- and sex-matched normal weight children were enrolled and treadmill test was performed. Exercise tolerance, the time to target heart rate and continuous T-wave alternans (TWA) during treadmill test were compared between two groups. Results 　Compared with normal weight children, the exercise tolerance was decreased and the time to target heart rate was shortened, while the incidence of continuous TWA was increased in obese children and there was significant difference between two groups (P<0.01). Conclusions　Obesity may lead to cardiovascular dysfunction in childhood which should be concerned.