Abstract: In the supporting electrolyte containing4.0×10^-3Mthiosemicarbazide(TSC)and 0.04Mpotassium hydrogen phthalate(pH=4),a sensitive derivative peak wave has been obtained by using single-sweep oscillopolarography.The peak potential is-0.65V(SCE).The change of peak height with the concentration of cadmium(Ⅱ)is linear in the range from 8.9×10^-8 to 3.6×10^-6M.The mechanism of the wave has also been studied in detail.The chronocoulometric study shows that in the presence of TSCthe adsorption of Cd(Ⅱ)on the surface of Hg electrode is direct adsorption of Cd(Ⅱ)-TSCcomplex and the adsorbed species is Cd(TSC)²⁺.