Abstract: Cyprinid herpesvirus 2 (CyHV-2) is the pathogen of herpesviral hematopoietic necrosis of Carassius auratus. It is a double-stranded DNA virus that can infect goldfish, crucian carp and its varieties. This study investigated the effect of CyHV-2 ORF57 on viral replication in Spinal cord tissue cell lines of Carassius auratus gibelio (CSC). Lipofectamine 2000 was used to transfect siRNA. Three pairs of siRNAs of CyHV-2-ORF57 gene were transfected into CSC cells to evaluate the effect of ORF57 on viral replication and cytopathic effect (CPE). Real-time PCR analysis revealed that ORF57-siRNA-2 had the greatest suppression of ORF57 expression with a 33.55% (P<0.01) reduction at 48h associated with the strongest inhibitory effect. All three ORF57-siRNAs delayed the time and intensity of CyHV-2 cytopathogenic effect, with the inhibition time up to 120h. The results of TCID₅₀ showed that ORF57-siRNAs reduced the titer of the virus, and ORF57-siRNA-2 decreased the virus stock solution TCID₅₀ 10^8.487/mL to 10^6.776/mL. This study show that ORF57 can mediate the CPE and replication rate of CyHV-2. This study provides a reference for the antiviral treatment based on siRNA technology and the construction of low virulent strain of CyHV-2.