Objective To evaluate the effects of inhaled nitric oxide(INO) in the early period after Fontan operation. Methods Twenty children receiving INO [(10 ～ 25) × 10 -6] after fight heart bypass for congenital heart disease were evaluated. The changes of hemodynamic and respiratory parameters were observed at two different intervals. The levels of methemoglobin (MetHb)and nitrogen dioxide(NO2)were monitored. Results In INO therapy group,CVP decreased from (20.8±4.8) mm Hg to (14.3±1.8) mm Hg,TPG decreased from (16.3 ±3.0) mm Hg to (8.8±2. 1) mm Hg,PaO2/FiO2 increased from (70.3±16.9) mm Hg to (120.5 ±14.0) mm Hg,and arterial oxygen saturation increased from 0. 78 ±0. 14 to 0. 91 ±0. 09 ,blood lactic acid level decreased from (3.98 ± 0. 86) mmol/L to (1.29 ± 1.60) mmol/L. No toxic side effect was observed. Conclusion INO has no significant long-term effect on patients after Fontan operation, but it can improve respiratory function, and reduce the incidence of low cardiac output syndrome and high cava pressure caused by reactive elevation of pulmonary vascular resistance in the early postoperative period after Fontan operation.