Abstract: A new system of Cu(Ⅱ)-Imidazole for the determination of trace copper by polarography is proposed.In a supporting electrolyte containing 0.2mol/L NaOH,a sensitive adsorptive-complex wave of this system was obtained by single-sweep polarography.The peak potential of the polarographic wave was -0.59V vs.SCE. The linear relationship between v/ave height and the concentration of coppre held in the range of 3.1×10^-8~1.6×10^-6mol/L.This method has a better selectivity for it is satisfactory in the determination of trace copper in waste water or surface water.The character of the polarographic wave was studied by cyclic voltammetry, normal pulse polarography and some other methods. The results indicated that the polarographic wave is an adsorptive wave of complex with weakly adsorbed reactant. The .adsorptive species is Cu(Imid)₃²⁺, which was inferred from contrast experiment with the. theoretical calculation.