Emodin is an important component of traditio na l Chinese herb, Rhubarb(Da Huang),and has various efficacies, including suppress ing bacterial, anti-inflammation,protecting function of the liver and the kidney ,inhibiting platelet aggregation,improving microcirculation,anti-cancer, and sho ws good values in clinical application. This article reviews developments in its pharmacological action and mechanism and provides theoretical evidences for exp loiting of Emodin.