Inhibitory effect of water and ethyl acetate extract of 60 kinds of herbal medicines was investigated on ${eta}-glucuronidase$. Among water extract of them, Galla Rhois had the most potent ${eta}-glucuronidase-inhibitory;activity$. Termaliae Fructus, Amomi Tsa-ko Fructus and Arecae Semen were also potent inhibitors. Among ethyl acetate extract of them, Galla Rhois had the most potent ${eta}-glucuronidase-inhibitory;activity$. Nelumbinis Semen. Ephedrae Radix and Termaliae Fructus were also potent inhibitors. The extract of Galla Rhois had potent hepatoprotective effect on $CCl_4-induced$ hepatotoxicity of rats. These results suggest that the ${eta}-glucuronidase$ seems to be closely related to the liver injury, which could be prevented by the inhibitor of ${eta}-glucuronidase$.