Abstract: Objective To evaluate the surgical effect of severe congenital heart disease with pulmonary infection in infants with low body weight(≤5 kg) and summarize the clinical experience. 
Methods A total of 110 cases of severe congenital heart disease with low body weight(≤5 kg) in cardiac surgery department were collected. According to the preoperative lung conditions, all the cases were divided into the infected group and the non-infected group, including 64 cases in the infected group and 46 cases in the non-infected group. To study the early results of surgical correction of low weight critical congenital heart disease complicated with pulmonary infection. The perioperative complications of the infected group and the non-infected group were analyzed. 
Results There was no statistically significant difference with the two groups in intraoperative aortic block time, extracorporeal circulation time, and the secondary intubation group, but the number of cases, duration of mechanical ventilation(≥48 h), duration of positive inotropic drug time and duration of ICU(≥72 h) in the infected group was higher than that in the non-infected group, with statistically significant differences(P＜0.05). There was no statistically significant difference in the incidence of pathogen infection between two groups(P＞0.05). After operation, white blood cells, C-reactive protein and procalcitonin in 2 groups were all increased first and then decreased to normal levels. There were statistically significant differences in the interaction between groups, time points, and time points between groups(P＜0.05). 
Conclusion The critical congenital heart disease in infants was complicated with pulmonary infection before operation, and the perioperative complications were higher than those in the non-infected group, but the early operation effect was good. The key to the treatment is to strengthen the protection of myocardium and lungs, improve the operation technique, shorten the operation time, strengthen anti-infection and postoperative monitoring, and deal with all kinds of postoperative complications in time.

Key words: heart diseases； infection control； , infant