Abstract: Objective To evaluate the effect of large tidal volume（VT） ventilation on ventilator-associated pneumonia（VAP）during perioperation. Methods Twenty-six VAP patients with good heart and lung function and stable general condition after operation were selected and randomly divided into control group and treatment group.The patients were observed for 5 days,during which the heart and lung function,small tidal volume and other ventilation parameters were not changed for the patients in control group,while large VT and slow respiratory rate（RR） ventilation were used for the patients in treatment group. Results In treatment group,the VT was increased from（7.8±0.6）ml/kg to（13.5±1.1）ml/kg,the RR was decreased from（23±6）times/min to（16±3）times/min,the peak airway pressure was decreased from（29.2±2.3）cmH₂O to（22.6±2.5）cmH₂O,the PaO₂ was increased from（77.4±5.8）mmHg to（110.6±11.7）mmHg with no significant change of PaCO₂ and pH after 1h,the body temperature was decreased from（38±0.5）℃ to（37.6±0.4）℃ after 24h and further decreased to（36.6±0.7）℃（P＜0.001） after 5 days,the number of white blood cells was decreased from（15.3±3.2）×10⁹/mm³ to（8.6±2.5）×10⁹/mm³,the infiltrated area of lung was decreased from 44%±9% to 18.8%±3.6% after 5 days（P＜0.001 or P＜0.05）.In control group,however,these parameters were not significantly changed except for the infiltrated area of lung（P＜0.05）. Conclusion Large VT mechanical ventilation can rapidly improve hypoxemia and pulmonary infection in VAP patients during perioperation.