The present invention provides a novel nucleoside phosphoramidate compound, or a stereoisomer, salt, hydrate, solvate or crystal thereof for the treatment of Flaviviridae family viral infection, especially hepatitis C viral infection. The present invention also provides the pharmaceutical composition comprising a compound of the present invention, or a stereoisomer, salt, hydrate, solvate or crystal thereof and a use of the compound or the composition of the present invention in the treatment of Flaviviridae family viral infection, especially hepatitis C viral infection. The compound of the present invention has a good anti-HCV effect.
