Abstract: This paper describes the optimum conditions for determination of Cu ( Ⅱ) which catalyzes the reaction between peroxidisulphate and iodide that monitored by iodide selective electrode. Anew method of standard calibration and comparison was suggested simultaneously. At a fixed-time procedure, the variation of poten-tial(ΔmV) is linearly related to Cu ( Ⅱ ) Cone, in the range of 2.5 to 25 ng/ml.