Abstract: Objective To understand the AmpC -lactamases genotype of the plasmids mediated in Klebsiella pneumoniae causing nosocomial lower respiratory tract infection among elder patients and provide evidence for the surveillance of the bacteria producing AmpC -lactamases and the prevention and control of related infection. Methods Cefoxitin disk diffusion test was conducted to detect the phenotype of AmpC -lactamases, and AmpC -lactamases was confirmed by dual paper phenotypic method. The plasmids was extracted from bacterium with minipreps kit UNIQ-10. Polymerase chain reaction (PCR) and DNA sequencing were conducted to detect the genotype of AmpC -lactamase of the plasmids, Results A total of 17 K. pneumoniae strains producing AmpC -lactamase genotype DHA-1 were detected, accounting for 17.5%. Conclusion Klebsiella pneumoniae producing plasmid-mediated AmpC -lactamase circulated in Linhai County Traditional Chinese Medicine Hospital, and the plasmid-mediated AmpC -lactamase mainly belonged to genotype DHA-1.