All of the sequences of β2nodavirus were collected from GenBank and divided into four genotype groups , SJNNV (Striped jack nervous necrosis virus) group , BFNNV (Barfin flounder nervous necrosis virus , BFNNV) group , RGNNV (Redspotted grouper nervous necrosis virus) group and TPNNV (Tiger puffer nervous necorsis virus) group. The similarity among the sequences in the same genotypes was more than 85 % and the similarity among different genotypes was less than 66 %. Four pairs of primers were designed using the softwares of Premier and Sequencher. The four genotypes were identified and discriminated by RT2PCR with these primers.Quarantine and supervision were conducted on the larvae of marine fish imported from Taiwan through Shenzhen port and the marine fish cultured in Guangdong and Fujian provinces . The VNNV of RGNNV genotype was detected in the samples of imported larvae of marine fish. The same genotype was also detected in diseased adult fish and larvae of groupers ( Epinephellus sp . ) cultured in Guangdong and Fujian provinces . The similarity of gene sequences among all of these amplification products was more than 96. 5 % and the similarity of deduced amino acid sequences between these products and Malabaricus nervous necrosis virus (MNNV) was 100 %.