The polarographic behaviour of cadmium complex with murexide,including the calculation of stability constant,has been studied in detail in this paper.Cadmium and murexide waves appear at about -0.45V and -0.10V respectively in separated solution.Four reducible waves appear at about -0.10V,-0.25V,-0.45V and -0.6V respectively in a mixed solution of cadmium with murexide under certain conditions.It has been proved that the first wave is the result of the reduction of free murexide,the second is of murexide bound in the complex,the third is of free cadmium ion,and the fourth is of cadmium bound in the complex.The mechanism of the complex formation and the electrode reaction was discussed.The stability eonstant and the diffusivity of the oomplog wero calculated.