Abstract: Grass carp reovirus (GCRV) is a double-stranded RNA (dsRNA) virus that causes grass carp hemorrhagic disease (GCHD), resulting in substantial economic losses in aquaculture. Based on genomic and epidemiological characteristics, GCRV strains are classified into three genotypes (GCRV-Ⅰ—Ⅲ), among which genotype Ⅱ (GCRV-Ⅱ) being the predominant causative agent of GCHD outbreaks. Although GCRV-Ⅱ strains share over 95% nucleotide and protein sequence similarity, they exhibit marked differences in virulence and pathogenic effects on host metabolism. This review summarizes recent advances in the molecular and epidemiological characteristics of GCRV-Ⅱ, highlights key findings on strains with varying virulence, and discusses progress in diagnostic techniques and vaccine development. Future research directions are proposed to facilitate effective prevention and control strategies for GCHD.