Objective To evaluate the effect of selective decontamination of digestive tract(SDD)on preventing ventilator-associated pneumonia by Meta-analysis based on theory and method of evidence-based medicine.Methods Six medical databases (PubMed,Excerpta Medica Database [EMBASE],China Biology Medicine disc[CBMdi-sc],China National Knowledge Infrastructure[CNKI],VIP database,from 1995 to 2014,and Cochrane Library of issue 12,2014 )were searched,literatures were selected,data were extracted,Meta-analysis was performed by using RevMan 5.3 software.Results 13 literatures were included (2 676 patients were involved),Meta-analysis revealed that the incidence of VAP in treatment and control group was 20.68% and 35.99% respectively (OR and 95%CI ,0.40 [0.28,0.56],P <0.001 ),the mortality rate of patients with mechanical ventilation in treatment group and control group were 20.60% and 20.03% respectively (OR and 95%CI ,0.99 [0.81 ,1 .20],P =0.91 ). Conclusion SDD can reduce the incidence of VAP in patients with mechanical ventilation,but can’t reduce mortali-ty rate.