ionic equilbria of nickel chloride in hydrochloric acid solutions were analyzed by considering chemical equilibria, mass and charge balance equations. The activity coefficients of solutes were calculated by using Bromley equation. It was found that most of species containing nickel existed as $Ni^{2+}$ 와 $NiCl^{+}$. The mole fractions of nickel hydroxides were very low in the con-centration ranges considered in this study and the mole fraction of$Ni_4$ $(OH)_{4}^{4+}$ increased greatly with the pH of the solution. The pH values of $NiCl_2$ $-HCl-NaOH-H_2$O system at $25^{circ}C$ calculated in this study agreed well with those experimentally measured up to ionic strength of 9.4m.