Objective To evaluate the antiviral activity of oseltamivir phosphate，ribavirin and rimantadine hydrochloride on influenza A (H1N1) in vitro. Methods Drugs diluted in FCS-free DMEM media supplemented with 2 μg /mL TPCK-treated trypsin was applied to confluent MDCK cell monolayers for 1 h prior to addition of virus，at a challenge dose of one hundred times of the TCID50 . The IC50 of drugs were calculated using neutral red assay after 3 days treatment at 34℃ .Results The therapeutic index (TI) of oseltamivir phosphate against influenza A ( H1N1) virus was 61. 90，ribavirin was 42. 86，and rimantadine hydrochloride was 6. 22. Ubenimex was lower than 1. 00. Conclusions Influenza virus is sensitive to oseltamivir phosphate and ribavirin. The antiviral effect of rimantadine hydrochloride is significantly lower than that of oseltamivir phosphate and ribavirin.