Abstract: OBJECTIVE To explore the molecular gene characteristics of highly virulent Klebsiella pneumoniae in patients with respiratory system infection and observe the clinical characteristics. METHODS A total of 524 patients with K. pneumoniae respiratory system infection who were treated in Jiaozuo People′s Hospital from Sep 2017 to Oct 2018 were recruited as the study objects, 148 patients who had highly virulent K. pneumoniae infection were assigned as the observation group, and 376 patients who had common K. pneumoniae infection were set as the control group.The clinical characteristics of the two groups of patients such as age, gender and underlying diseases were analyzed, the distribution characteristics of the molecular genes such as plasmid specific sequence（rep）, Pod synthesis factor（rmpA） and iron carrier aerobactin（iuc） were observed and compared between the two groups; the score of quality of life was compared between the two groups of patients, and the drug resistance rates were compared between the highly virulent K. pneumoniae strains and the common K. pneumoniae strains. RESULTS There were no significant differences in the age, gender, clinical sources, underlying diseases, hospitalization duration and mixed bacteria cultured from sputum between the two groups of patients.There were significant differences in the highest body temperature and result of chest CT examination between the two groups of patients（P＜0.05）.As compared with the distribution characteristics of the molecular genes, the positive rates of rep, rmpA and iuc of the observation group were respectively 89.86%（133）, 79.73%（118） and 91.89%（136）, significantly higher than those of the control group（P＜0.05）.The total score of quality of life of the observation group was（83.24±12.27） points, significantly lower than（115.59±27.04）points of the control group（P＜0.05）.The drug resistance rate of the highly virulent K. pneumoniae strains to ampicillin was 90.54%, the common K. pneumoniae strains 97.60%. CONCLUSION The quality of life of the patients with highly virulent K. pneumoniae respiratory system infection is poor, and the positive rate of virulence plasmid pLVPK gene of the highly virulent K. pneumoniae strains is higher than that of the common K. pneumoniae strains.