Abstract: Objective To explore the mechanisms of imipenem resistance inKlebsiella spp. and the transmission of Klebsiella pneumoniae Carbapenemase-2（KPC–2） gene in Klebsiella species. Methods The imipenem resistant Klebsiella pneumoniae and Klebsiella oxytoca were isolated in the West China Hospital of Sichuan University in 2009/2010 and 2012/2013. Their minimal inhibitory concentration (MIC) was determined by agar dilution method. CARB ChromID plate and improved Hodge test were undertaken to detect carbapenemases resistant phenotype. PCR method was used for detecting KPC-2 gene. Plasmid transmission was detected by plasmid conjugation tests. The homology of the plasmids and the strains was analyzed using random amplified polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus PCR（ERIC-PCR） methods. Results Three strains of Klebsiella oxytoca collected in 2009/2010 and 7 Klebsiella pneumoniae collected in 2012/2013 developed carbapenemases resistance, all of which carried KPC-2 gene. The 3 KPC-2 positive plasmids isolated from Klebsiella oxytoca transited to recipient organisms and showed homology with the 7 KPC-2 gene positive plasmids isolated from Klebsiella pneumoniae. The ERIC-PCR showed homology of the 7 KPC positive Klebsiella pneumoniae. Conclusion Carbapenemases inKlebsiella spp./i> with expressed KPC-2 gene contribute to the development of resistance in this hospital. The transmission of KPC-2 plasmid in Klebsiella oxytoca may cause imipenem resistance in Klebsiella pneumonia. The horizontal transmission may be the main mechanism in the spread of imipenem resistance inKlebsiella spp./i>