Objective  To determine the long-term effect of pressure support ventilation (PSV) on experimental lung injury. Methods  The animal model of acute lung injury (ALI) was established by repetitive lung lavage for 20 healthy adult female rabbits. Rabbits were randomly divided into the PSV group (n=10) with the pressure level of tidal volume>4 mL/kg and respiratory rate of <40/min and controlled mechanical ventilation (CMV) group (n=10) with the pressure level of tidal volume of 4 mL/kg and respiratory rate of 20/min. The positive end-expiratory pressure of two groups was set at 10 cmH₂O. Blood gas analysis and determination of ventilation-perfusion (V_A/Q) distribution were performed at the onset of ALI and 2, 4, 8, and 12h after the onset of ALI. Results  The oxygenation of PSV group improved remarkably because the pulmonary shunt remarkably decreased and the area with normal V_A/Q ratio increased. Compared with the PSV group, the pulmonary shunt of CMV group significantly decreased (P<0.05). Conclusion  PSV remarkably improves the gas exchange by reducing the inequality of V_A/Q in the animal model of ALI. However, as far as the improvement of V_A/Q distribution is concerned,  CMV is more effective than PSV.