We aimed to explore the effects of perioperative exercise on cardiorespiratory endurance in children with congenital heart disease (CHD) in plateau areas after surgical repair. Fifty children with CHD in the plateau admitted to our hospital were randomly divided into the exercise and control groups. The exercise group received a perioperative exercise intervention beginning within 24 h postoperatively, while the control group received routine nursing and treatment alone. To assess the 6 min walk distance (6MWD) at baseline and at end of intervention, children participated in a 6-min walk test before cardiac repair and at 1 week after general ward transfer. A subset of children in the study underwent the cardiopulmonary exercise test pre-operatively. The 6MWD of children with CHD at baseline was positively correlated with the peak oxygen uptake pre-operatively. No significant difference was reported in the preoperative baseline data of both groups. The 6MWD of the exercise group was significantly higher than that of the control group. Early exercise therapy after cardiac repair could significantly improve the cardiorespiratory endurance and exercise capacity of children with CHD in plateau areas.