ObjectiveTo explore the method that can block the infection route from stomach to lung so as to reduce the incidence of ventilatorassociated pneumonia (VAP) in neonates.MethodsNeonates with mechanical ventilation were randomly divided into two groups，the experimental group (38 cases) were given Bifidobacteria by nasogastric feeding, control group (43 cases) were given nothing, prospective survey was performed on the  incidence of VAP, gastric juice PH, gastric bacterial colonization, the homology between  gastric bacterial colonization and  VAP pathogen.ResultsThe VAP incidence of experimental group and  control group was 13.16 %(5/38) and 46.51% (20/43) respectively,there was significant difference between two groups （χ2=10.52,P＜0.01）.The onset time of VAP in  experimental group （5.4±2.07d）was later than that of  control group(4.25±1.00d) (t=3.24,P<0.01). The ratio of experimental group that gastric juice dropped to pH ≤3 was higher than that of control group(46.51%)（χ2=12.47,P＜0.01）; and the ratio of gastric bacterial colonization in experimental group(31.58%) was lower than that in control group(74.42%)（χ2=14.42,P＜0.01）.The homology ratio between VAP pathogen and colonization bacteria in experimental group (40.00%) was lower than that  in control group(75.00%) (χ2=8.00,P＜0.01）. The univariate analysis of risk factors showed that Bifidobacterium use and gastric bacteria  juice PH≤ 3 were protective factors , but gastric bacterial colonization was the risk factor. OR and 95% CI were statistically significant.ConclusionBifidobacterium can reduce gastric juice PH of neonates and inhibit gastric bacterial colonization . The onset time of VAP can be delayed, the incidence of earlyonset of VAP can be reduced effectively.