Study on the feasibility of EDI device, whose dilute departments were filled with cation exchange resins and feed water was low concentration Ni₂ solution, for the treatment of low-concentration heavy-metal wastewater. The effects of operating voltage and dilute flow flux on the separation performances EDI processes were investigated. With the feed solution whose Ni²⁺ concentration was 50 mg·L^-1 and pH was 4.5, the results show that the out dilute Ni²⁺concentration was lower than 2 mg·L^_-1 and the Ni²⁺ concentration of out concentrate could higher than 900 mg·L^-1 when operating voltage was 25 v and dilute flow flux was 20 L·h^_-1.