Preferential transport behaviors of metal ions for ternary ions system through a cation exchange membrane were studied in a stirred batch dialyzer. Cu2+-Fe3+-Ni2+ was chosen for the experimental investigation. Oxalic acid, malonic acid, citric acid, and ethylenediaminetetraacetic acid were employed as a complex agent used in the investigated solution in order to increase the discrepancy between transport fluxes of metal ions. The experimental results show that the order of effective complex agents is malonic acid > citric acid > oxalic acid > ethylenediaminetetraacetic acid. The preferential transport behavior of metal ions depends on the stoichiometric ratio of the complex agent to metal ions and the pH value of the feed solution, but is independent of the concentration of counterion in the stripping phase. The optimal results of J(Ni) : J(Cu) : J(Fe) can be attained about 30 : 10 : 1.