Abstract: AIM: To study the effects of inhaled Nitric Oxide (NO) on pulmonary function and pulmonary surfactant during cardiopulmonary bypass in infants. METHODS: Thirty infants with congenital heart disease with the high degree of PH were randomly divided into two groups: control group (n=15) and NO group (n=15). From throughout the cardiopulmonary bypass（CPB）, 40 μl/L NO was inhaled in NO group. Before CPB and at 1, 5 and 10 min after aortic declamping, air tube was lavaged by small amounts of normal saline, the levels of TPL, SatPC and TP were determined and the values of SatPC/TPL and SatPC/TP were calculated. RESULTS: The levels of SatPC/TPL and SatPC/TP post-operation were lower than those before CPB (P<0.01) and the decreased formants of SatPC/TPL and SatPC/TP in control group were higher than those in NO group. CONCLUSION: Lung ischemia-reperfusion injury is obvious during CPB in infants and manifests as sub-clinical pulmonary function injury. Inhale 40 μl/L NO has marked protective effect on the lung function during CPB.