The modern instrumental analysis methods do not always allow direct determination of trace amounts of elements due to influence of the matrix composition of the sample. New complex adsorbents based on aminopolystyrene functionalized with azo-phenolic chelating groups applied for preconcentration of Ni(II) ions in its aqueous solutions. Optimal parameters affecting on the adsorption efficiency determined. The best adsorbent selected for subsequent tests. Dissociation constants of an adsorbent determined. The adsorption isotherm evaluated and the kinetics data analyzed. Thermodynamic parameters studied. The structure of the complex formation suggested. We found out that PSAPH-SO3H adsorbent has the best kinetic characteristics for nickel adsorption; at 25℃, 98.9% recovery achieved in 30 min. The Langmuir isotherm gives better fit to adsorption isotherm results. The adsorption of Ni(II) ions obeyed to pseudo-second order model. The thermodynamic parameters clarify that the spontaneous and endothermic nature of adsorption. The ionization stage of -N=N-group=4.27, of SO3H group=6.36 and of -OH group=7.95. The results can be used in the complex compound chemistry for the development of procedures for treatment of Ni2+ ions from naturally-occurring and industrial materials.