Abstract: Vibrio vulnificus is an important pathogen.When eating infected fish,human will suffer from serious disease.To date,many potential virulence factors of Vibrio vulnificus have been identified. Among the reported factors,Siderophore is a well-known crucial virulence factor.In this study,the siderophore- producing strains were screened by using MKB( Modified King B)medium which isolated from the seawater.MKB- CAS( Chrome azuorl S) overlay plate method and UV- VIS Spectrophotometer were used for the screening of high yield siderophore- producing strain and detection of SU( siderphore units) respectively.V.vulnificus Y8 strain was optimized which had the highest siderophore- producing capacity. The optimization of significant factors on SU including the initial p H,medium capacity and nitrogen ratio( C / N) was determined by response surface methodology. These results indicated that the value of SU was expected to 90.7404% under the optimum condition of initial pH7.84,medium capacity of 81.53 m L and C / N of 3.06.Three parallel verification results indicated that the maximum SU value was consistent with the mean SU value and the optimized SU value was increased by 23.73% compared to the previously measured value. The best optimization conditions was obtained by using response surface methodology which would lay the foundation of the further study in the future.