As a leading cause of respiratory disease,influenza A virus (IAV) presents a pandemic threat in annual seasonal outbreaks.Given the limitation of existing anti-influenza therapies,there remains to be a requirement for new drugs.Compound Yi-Zhi-Hao pellet (CYZH) is a famous traditional Chinese medicine (TCM) used in the clinic,whose formula has been recorded in Complication of National Standard for Traditional Chinese Medicine to treat common cold.In this study,we found that CYZH exhibited a broad-spectrum anti-influenza activity and inhibited the expression of viral RNA and proteins in vitro.Mechanistically,CYZH had no inhibitory activities against viral protein hemagglutinin and IAV RNA-dependent RNA polymerase.Instead,it induced activation of erythroid 2-related factor 2 (Nrf2) and nuclear factor kappa B (NF-κB),which subsequently upregulated heme oxygenase-1 (HO-1) expression.Also,CYZH protected cells from oxidative damage induced by reactive oxygen series.In conclusions,CYZH inhibits IAV replication in vitro,at least partly by activating expression of the Nrf2/HO-1 pathway.