Abstract: This study aims to determine intra-genomic 16S rRNA gene copy number of Vibrioharveyi strains by a method of fluorescent quantitative PCR. Vibrio strains were identified by multilocussequence analysis based on 16S rDNA, pyrH, rpoA and recA. A standard plasmid, harboring fragments of 16S rDNA and the single copy gene gyrB from V. harveyi type strain, was constructed. A fluorescent quantitative method was established and used to determine the intra-genomic 16S rRNA gene copy number of the tested 6 strains, the type strains of V. harveyi and V. harvei ATCC BAA-1116 as a reference, whose 16S rRNA gene copy number is well known. All the 6 tested Vibrio strains were identified as V. harveyi. The copy number of 16S rRNA gene in strain ATCC BAA-1116 was 11, consistent with the known values. The copy numbers of strain MCCC 1H00031T, SXB-C, SCB-4, NBV00029, NBV00035, NBV00039 and NBV00269 were 9, 12, 13, 12, 11, 13 and 9, respectively. Fluorescent quantitative PCR method is a simple and reliable for determining 16S rRNA gene copy number within genome. Intra-species variation of 16S rRNA gene copy number within V. harveyi might be of ecological significance for their adaptation to fluctuant coastal niches.