The electrochemical behaviour of the anticancer herbal drug emodin was investigated by cyclic voltammetry (CV) at glassy carbon electrode. In 0.05M NH 3 -NH 4 Cl (50% ethanol, pH 7.2) buffer solution, a pair of quasi-reversible redox peaks at potentials of Ep1=−0.688V and Ep2=−0.628V and one irreversible anodic peak, which was a typical anodic peak of emodin, at Ep3=−0.235V appeared at a scan rate of 100mV/s. The irreversible anodic peak currents are linearly related to the emodin concentrations in a range from 8.9×10 −8 M to 7.8×10 −6 M with a pre-concentration time of 80s under −0.620V. Using the established method without pretreatment and pre-separation, emodin in herbal drug was determined with satisfactory results. Moreover, the electrode process dynamics parameters were also investigated by electrochemical techniques.