Abstract: In order to establish a simple, rapid, sensitive and specific method for detection of the SB strain of Ostreid herpesvirus-1(OsHV-1), a cross priming amplification(CPA)assay was developed based on primers developed according to the conserved regions selected across the whole genome sequences of the SB strain of OsHV-1.Then the reaction temperature, time and concentrations of dNTPs and Mg²⁺ were optimized.Our results showed the optimum temperature and time of the assay were 63 ℃ and 60 min, and the optimum concentration of dNTP and Mg²⁺were 1.4 mmol/L and 6 mmol/L respectively.The CPA assay was highly sensitive with detection limit approximately 30 copies recombinant plasmid DNA per μL.The assay was also highly specific for OsHV-1-SB detection, with no cross-reactions was found when acute viral necrosis virus, abalone herpes viruses, Perkinsus sp., Bonamia sp., Martelia sp., white spot syndrome virus and Vibrio parahaemolyticus were used as controls.The prevalence of OsHV-1-SB in 22 blood clams, Scapharca broughtonii, collected from Gyeongsangnam-do in Korea, Shandong and Liaoning Province in China were detected with the CPA assay established in this study.The results showed that the CPA assay is a simple, rapid, sensitive, specific and reliable technique.Additionally, since the results of CPA assay could be read directly through centrifugation of the reaction mix or adding GeneFinder^TM to the mix, this assay can be used in shellfish farms and local laboratories with poor conditions.