Objective To investigate the effects of exogenous pulmonary surfactant （PS） on ventilation weaning and respiratory mechanics in infants with acute lung injury（ALI） after cardiopulmonary bypass （CPB）.Methods Twelve infants underwent cardiopulmonary bypass cardiac surgery committed with ALI and difficulty in weaning from ventilation were included in this study.Exogenous PS was used in the treatment via intra-tracheal administration.The changes of blood gas，respiratory mechanics and the conditions of ventilation weaning were observed.Results After intra-tracheal PS administration，spontaneous breath remained steady；spontaneous respiratory rate significantly decreased from，tidal volume of spontaneous breath increased significantly.Three concave sign disappeared and koilosternia was alleviated.PaCO2 value decreased significantly and peak inspiratory pressure（PIP） decreased from （36.18±10.25）cm H2O to （25.11±5.14）cm H2O （Plt;0.01）.Static lung compliance （Cstat） increased from （1.49±0.65）mL·cm H2O-1·kg-1 before treatment to （1.95±0.50） mL·cm H2O-1·kg-1 6 h after treatment （Plt;0.01）；and airway resistance （Rstat）decreased from （128.17±26.34） cm H2O·L-1·s-1 before treatment to （78.56±18.22） cm H2O·L-1·s-1 6 h after treatment （Plt;0.01）.All 12 infants weaned from ventilator successfully.Conclusion Combined with PS intra-tracheal treatment，lung protective ventilation strategy can significantly improve parameters of respiratory mechanics，increase dynamic lung compliance，decrease airway resistance，which can decrease the breathing effort of the infants and make it easy to wean from ventilator.