Abstract: Objective To analyze the extracorporeal circulation in patients during hypothermic open intra-cardiac surgery for beating heart and its clinical significance. Methods Extracorporeal circulation perfusion during hypothermic open intra-cardiac surgery for beating heart in 436 patients admitted to our hospital in March 1999-May 2009 was retrospectively analyzed. The patients were divided into children group with their age≤12 years （n=263） and adult group with their age ＞12 years（n=173）. Blood flow volume, blood pressure and temperature were compared during extracorporeal circulation in the two groups. Results The blood flow volume was significantly greater in children group than in adult group（P＜0.01）. However, the mean arterial pressure was lower in children group than in adult group （P＜0.01）. No significant difference was found in temperature and hypothermic open intra-cardiac surgery time during operation between the two groups. The 436 patients were discharged from hospital after complete recovery. Conclusion Hypothermic open intra-cardiac surgery for beating heart under extracorporeal circulation is safe for patients with simple congenital heart disease.