Provided are a novel nucleoside phosphoramidate compound, stereoisomer, salt, hydrate, solvate or crystal thereof for treating flaviviridae virus, in particular a hepatitis C virus infection. Also provided are a pharmaceutical composition containing the compound, stereoisomer, salt, hydrate, solvate or crystal thereof, and uses of the compound and composition for treating the flaviviridae virus, in particular the hepatitis C virus infection. The compound has a good anti-HCV effect.