Abstract: Objective: To investigate the efficacy and safety of aerosol inhalation of polymyxin B in treatment of ventilator-associated pneumonia caused by MDR. METHODS: Head-to-head comparisons were conducted to investigate the efficacy and safety of VAP caused by MDR with nebulization of polymyxin B and polymyxin E atomization and polymyxin E intravenously. RESULTS: The effective rate of aerosolization with polymyxin B was 76.7%, which was better than the inhalation of polymyxin E and intravenous infusion of polymyxin E. The average treatment time was 7.3±2.1 days. And serum PA, PCT, and TNF-a in polymyxin B patients were significantly higher than those in colistin E nebulization and intravenous infusion of polymyxin E patients. CD4+andCD4+/CD8+ were significantly superior to polymyxin E nebulization and polymyxin E infusion. There was no significant difference in the incidence of adverse reactions. Adverse reactions in all patients were mild, and adverse reactions disappeared after treatment and discontinuation. CONCLUSIONS: Polymyxin B nebulization and inhalation is more effective than intravenous injection of polymyxin E and polymyxin E in the treatment of VAP caused by MDR. The safety is comparable and no polymyxin B was found. The toxicity of the drug has significant clinical value.