Objecfive To investigate the association between bacteriology of airway secretions in acute onset chronic respiratory failure (ACRF) and its clinical prognosis.Methods The bacterial flora and antibiotic resistance in the airway secretions from 44 patients with 49 cases of ACRF were studied,the associations between bacteriology,antibiotic resistance and annual ACRF hospital admission frequency (ACRF≥2 or ACRF<2),its mortality were also explored.Results Positive rate of culture in airway secretions was 63.3%.Untraditional pathogens such as Pseudomonas Aeruginosa accounted for 80.7%.The bacterial yield of patients with ACRF≥2 was twice as that with ACRF<2 (P<0.01).Of the identified bacteria,61.3% displayed antibioticresistance,and there was signifi-cant prolongation of ventilation and hospitalization and increase of mortality in patients with antibiotic resistance(P<0.05).Conclusion There is a predominance of untraditional pathogens such as Pseudomonas Aeruginosa in bacteria from airway secretions of ACRF patients,positive yield and percentage of untraditional pathogens increased with the severity of chronic respiratory failure,infections caused by antibiotic-resistant strains led to higher mortality in ACRF.