Abstract: Objective To study the inhibitory eff ec ts of Astragalus membranaceus on herpes simplex virus type 1(HSV-1).Methods In the 2BS cells infected with HSV-1, the antiviral effect of Astragalus membranac eus decoction was investigated by observing the inhibition of HSV-1-induced cyt opathic effect in response to treatment with the decoction.Results The half in hibition concentration (IC50) and minimal inhibition concentration (MIC) of Astr agalus membranaceus were 0.98 and 1.95µg/ml respectively, with the therapeutic index (TI) of 128.Conclusion Astragalus membranaceus has obvious HSV-1-inhibit -ing efficacy and low cytotoxicity.