Abstract: Electrochemical behavior of emodin was studied by cyclic voltammetry,and direct determination of emodin in rhuharb by linear scanning polarography was proposed without pre-separation.In a B-R buffer solution of pH 5.72,a sensitive polarographic peak of emodin was observed at the potential of -0.434 V (vs.Ag/AgCl).Linear relationship between values of peak current and concentration of emodin was obtained in the range of 1×10-6-1.5×10-5mol·L-1.It was shown that,at a low scanning rate,the reduction process of emodin is an quasi-reversible electrode process,controlled mainly by adsorption.