Objective To analyse the pathogenesis of ventilator associated pneumonia (VAP) and their resistance to antibiotics and to guide treatment with antibiotics. Methods A retrospective clinical study in 57 ICU patients with VAP was carried out from 2007.1 to 2007.10. The pathogens and their drug resistance were analyzed. Results A total of 145 pathogen strains were isolated and identified by bacterial culture. The pathogenic bacteria in VAP was the Gram-negative bacilli (GNB, 51.72%), Gram-positive bacteria (GPB, 26.21%), fungi (22.07%). The major bacteria was pseudomonas semginosa, staplyloeoccus sureus, candida albicans and klebsiella pneumoniae. Drug sensitivity tests indicated that the GNB had lower drug resistance to imipenem, levofloxacin, meropenam, amikacin; the GPB had lower drug resistance to teicoplanin, vancomycin, linezolid, fusidate, fosfomycin: the fungi had lower drug resistance, to itraconazole, amphotericin, fluconazole. Conclusions The major pathogens in VAP were GNB and fungi infection were increased in recent years. Epidemiology and drug sensitivity tests of pathogens must be consided when we treat VAP in ICU. Key words: ICU; Respiratory-associated pneumonia; Etiology; Susceptibility