Glycyrrhizic acid (GA) is a triterpenoid saponin glycoside from licorice roots and rhizomes, having a variety of pharmacological activities, but its solubility in water is poor. In this study, we got GA nanoparticle suspensions about 180 nm by SAS (supercritical antisolvent) process. Comparative anti HSV-1 (herpes simplex virus type 1) studies were undertaken using nano-GA (glycyrrhizic acid nanoparticles) with its ammoniated salt--- MAG (glycyrrhizic acid ammonium salt). The maximum noncytotoxic concentration of both nano-GA and MAG were 187.5 μM for BHK cells. MTT assay showed GA nanoparticle suspensions exhibited better anti-HSV activities compared to MAG, especially during replication period. Morphology of HSV-1 observed by TEM (transmission electron microscopy) significantly changed with nano-GA treatment. TEM images showed that the envelope of HSV-1 was damaged and shedded.