Salt lake brine is an abundant lithium resource and has great developing value and potentiality. But the Mg/Li ratio of some salt lakes in China and Dead Sea in Jordan is extremely high. In this study, electrodialysis (ED) with monovalent selective ion-exchange membranes was used to investigate the separation performance of Li+/Mg2+ from synthetic multinary mixture. The effects of operating conditions on the lithium recovery, permselectivity, and Mg/Li rail) of the product were evaluated. The results indicate that ED with monovalent selective ion-exchange membranes has a significant separation effect on Li+/Mg2+. When the optimized parameters were used in ED, the Mg/Li mass ratio of the product stream was reduced to 8.0 (18.8 times compared to a feed Mg/Li ratio of 150), and simultaneously, the Li+ recovery reached to 953%. Compared to nanofiltration, ED exhibited superiority both technically and economically for the fractionation of Li+/Mg2+. It was also verified that the presence of co-existing cations would not be detrimental to the feasibility of lithium extraction using ED. Meanwhile, the separation mechanism of ED process was discussed qualitatively. (C) 2016 Elsevier B.V. All rights reserved.