This study investigated the effect of the extract of Bupleuri Radix (BRE) on the infection of Madin-Darby Canine Kidney (MDCK) cells by anti-H1N1 virus. The effect of BRE on RANTES (the chemokine regulated on activation, normal T cells expressed and secreted) secretion in H1N1-infected A549 cells (human bronchial epithelial cells) was evaluated via quantative measurement of the changes in the cytopathic effects and by the ultraviolet (UV) absorbance at 600 nm. It was found that BRE was toxic to MDCK cells at a higher concentration while had a marked inhibitory effect on cell pathological changes at a lower concentration. Results also showed that BRE possessed more than 50% suppressing effect on RANTES secretion in H1N1-infected A549 cells at a concentration of 100 and 200 μg/ml. Our findings show that BRE has a significant protective effect on MDCK cells infected in a dose-dependent manner with an excellent suppressing effect on RANTES secretion, suggesting that BRE can be developed as an antivirus agent.