The aim of this study was to study the effect of infectious hematopoietic necrosis virus (IHNV) nucleic acid vaccine on the immune protection of Oncorhynchus mykiss and serum biochemical indices of Oncorhynchus mykiss. Cloning the glycoprotein gene (G) into pMD19-T vector, we transformed the linked product in DH5α, obtaining recombinant plasmid pMD19-T-G, and recovering the G gene fragment. The identified correct G gene fragment was cloned on eukaryotic expression vector pVAX1 using BamH I and Xho I cleavage sites to construct nucleic acid vaccine pVAX1-G. The recombinant plasmid pVAX1-G was injected into O. mykiss at a dose of 8 μg/ind. as pVAX1-G group, while 8 μg/ind. empty group, PBS control group and blank group were set up. Twenty-one days after immunization, an anti-virus experiment was carried out. After anti-virus, serum was collected and blood indexes were tested. The results showed that there were significant changes in 16 indexes in O. mykiss serum after the attack:glutamic-pyruvic transaminase (ALT), glutamate transaminase (AST), alkaline phosphatase (ALP), total bilirubin (TBIL), total bile acid (TBA), glucose (GLU), the urea (Urea), creatinine (CREA), total protein (TP), albumin (ALB) and globulin (GLO) were compared with normal O. mykiss, and the changes of 11 indexes in no-load group were more significant than those in pVAX1-G group. The cumulative death rate of pVAX1-G group was 19%(19/100)14 days after the attack, while that of no-load group and PBS control group was 62%(62/100) and 85%(85/100), respectively. The protective rate of pVAX1-G nucleic acid vaccine for O. mykiss was 78%. The results showed that pVAX1-G as a nucleic acid vaccine was helpful to reduce IHNV's injury to O. mykiss and had better immune protection effect against IHNV.