Abstract: Objective To investigate the mechanism of quinolone resistanceof Aeromonas spp. isolated from cdinical patients. Methods The Aeromonas strains isolated from feces specimen of diarrheal outpatients in Beijing Friendship Hospital during 2017 were subjected to the susceptibility test to quinolones by microbroth dilution method. PCR were performed to extract the mucleic acids of the strains.The genes of qui nolone-resistance-determining region ( QRDR) of Aeromonas species and plasmid-mediated quinolone resistance ( PMQR) on chromosome were analyzed by sequencing. Results Of the 111 collected strains, 7( 6.3% ) strains were resistant to ciprofloxacin ( CIP)-nalidixic acid (NAL), 54( 48.6%) were resistant to NAL, but sensitive to CIP, and 50( 45.0%) were sensitive to both CIP-NAL. The sequence of QRDR showed that Ser831le/Val/Tyr mutation on gyrA was screened in NAL-resistant strains. In addition to mutation of gyrA, Ser87lle mutation of gene parC was identifed in all NAL-CIP-resistant strains. In the 104 CIP-sensitive strains, Ser87Ile mutation of parC was only found in 7 strains. The results of PMQR gene sequencing for these strains showed that detectable rate of gene QnrS was 7.2% ( 8 strains), aac(6' )-Ib-cr was 6.3% (7 strains). Most of QnrS and aac(6' )-Ib-cr were found in CIP-resistant strains. PMQR-positive strains constuted 85.7% of the CIP-resistant strains. Concusion The Ser83 mutation of gene gyrA or QnrS may relate with low levels of quinolone resistance of these strains. The gene PMQR coupled with Sr831le/Val/Tyr mutation in gyrA and Ser87Ile mutation in purC may give rise to high level of quinol oneresistance for Aeromonas app.