Objective To study the incidence of ventilator-associated pneumonia(VAP)and antimicrobial resistance of pathogens in an intensive care unit(ICU).Methods The occurrence of VAP in hospitalized patients with mechan-ical ventilation>48 hours between January 2011 and December 2012 were investigated,species and antimicrobial re-sistance of pathogens causing early onset-VAP (E-VAP,mechanical ventilation≤4 d)and late-onset VAP(L-VAP, mechanical ventilation>4 d)were compared.Results A total of 1 76 patients were investigated,incidence of VAP was 44.32% (78 cases);With the prolongation of mechical ventilation,incidence of VAP increased gradually (χ2=52.561,P<0.001).The incidence of L-VAP was significantly higher than E-VAP (58.33% [70/120]vs 14.29%[8/56])(χ2= 30.02,P<0.001).A total of 178 pathogens were isolated,gram-negative bacteria,gram-positive bac-teria and fungi were 104(58.43% ),46(25.84% ),and 28(15.73% )isolates respectively;97(54.49% )multidrug-resistance/pandrug resistance organisms (MDRO)were isolated. MDRO isolation rate in L-VAP patients was high-er than E-VAP patients([58.86% ,n= 93]vs [20.00% ,n= 4]),resistance rate of major pathogens causing L-VAP was significantly higher than E-VAP patients(allP<0.05).Fungi infection only occurred in L-VAP patients,the total antimicrobial resistance rate was 12.14% .Conclusion The prolongation of mechanical ventilation can increase the incidence of VAP,and resistance rate of pathogen in L-VAP is high.