[Objective] To study the anti - influenza effect of Heat - clearing Mixture No.5. [Methods] Tissue culture techniques of MSCK and hemagglutination test were applied. [Results] The lowest concentration of the mixture to suppress influenza virus was 5mg/ml. [Conclusion] The Heat-clearing Mixture No.5 has significant effect on suppressing influenza virus. The hemagglutination test proved that this Chinese medicine could block the replication of influenza virus.