Hepatitis C virus (HCV) is an enveloped virus with a plus-stranded RNA genome.It contains a large open reading frame (ORF) encoding a polyprotein which can be proteolytically cleaved to structural and nonstructural proteins with different functions.The isolates of HCV show substantial nucleotide sequence variability distributed throughout the viral genome.HCV isolates can be classified into many genotypes and subtypes.Studies on HCV heterogeneity has an important guiding significance for the pathogenesis,epidemiology,diagnose and therapy of HCV.