In order to study the immuno-protective efficacy of GCRV-VP6 subunit vaccine,the recombinant expression vector pET28a(+)-VP6 was constructed by cloning vp6 gene of GCRV into the prokaryotic expression plasmid pET-28a(+).The results of SDS-PAGE and Western-blotting showed that the molecular mass of the recombinant VP6 protein was approximately 43 ku.The recombinant protein reached 20% of the total bacterial proteins,and was mainly in the form of insoluble bodies.The grass carp(60-120 g in body weight and 14-20 cm in body length)was immunized with 500 μg purified VP6 protein by Ni²⁺ affinity chromatography and antibody titers in the blood of fish were determined by means of indirect agglutination reaction on the 14th,21st,28th,49th and 70th days post-vaccination.The results showed that the specific antibody could be detected on the 14th day,reached peak on the 21st day and could be still detected on the 70th day after immunization.The fish in vaccinated group and control group were challenged with GCRV on 21st days after vaccine delivery and the relative survival rate in the vaccined group was 100%.These results provided important academic foundation for research and development of GCRV genetic vaccine.