The invention provides a spiro compound serving as a hepatitis C inhibitor, a drug composition and applications of the spiro compound and the drug composition in drugs. The compound is a compound shown in a formula (I) or a stereisomer, a geometric isomer, a tautomer, nitric oxide, hydrate, solvate, metabolite and pharmaceutically acceptable salt or prodrug of the compound shown in the formula (I). Besides, the invention also provides the drug composition comprising the compound, an application of the compound and the drug composition to inhibiting at least one of HCV (hepatitis C virus) replication and HCV protein functions, and an application of the compound and the drug composition to preventing, disposing, treating or alleviating HCV infection or hepatitis C diseases of patients.