Abstract: The adsorption characteristics of the nickel complex with dimethylglyoxime (DMG) Ni (Ⅱ)A₂ at the HMDE has been investigated It was found that between -0.20 and -0.90V (vs. SCE) Ni (Ⅱ)A₂ can be adsorbed fairly well at the HMDE and the relationship observed by voltammetry with linearly changing tension between the logarithm of the peak current and the logarithm of the sweep velocity is linear and has a slope of 0.98. Experimental peak currents show a Langmuir isotherm with the preconcentration time. The overall reaction of the adsorption voltammetry of nickel-DMG system, which can be divided into three parts, has been discussed. That is 1) Homogeneous reaction between different nickel species in solution, 2) Adsorption preconcentration process of Ni(Ⅱ)A₂, 3) Reduction of adsorbed Ni(Ⅱ)A₂, by irreversible charge transfer. The sensitivity of the method appears between 10^-9M and 10^-10M depending on the preconcentration time.