Abstract： Objective To investigate the multi-drug resistance of Klebsiella strains and its mechanism.Methods Twenty strains of Klebsiella were isolated from the Affiliated Hospital of Medical College,Ningbo University from October 2009 to March 2011,in which 18 isolates were Klebsiella pneumonia and 2 were Klebsiella planticola. Drug sensitivity was determined by K-B tests. Drug resistant genes gyrA,parC (chromosome mediated) and aac( 6′)-I b-Cr,qnrA,qnrB,qnrS,qepA (plasmid mediated) were amplified by PCR and verified by direct automated fluorogenic sequencing. Results Resistance to β-1actams,aminoglycosides and quinolones was observed in 20 strains,and resistant rates were all above 80％.Klebsiella planticola strains were sensitive to imipenem and meropenem.Mutations of gyrA and parC genes existed in 18 strains (90％),and the positive rates of aac (6') -I b-C r,qnrB and qnrS were 60％ (12/20),20％ (4/20) and 20％ (4/20),respectively.Conclusion The mutations ofgyrA and parC genes may be the main cause of the resistance to quinolones in these strains.