Charge mosaic (CM) membranes with semi-interpenetrating network structures were prepared by blending poly(vinyl alcohol) as a membrane matrix, poly(allyl amine) as a polycation and poly(vinyl alcohol-co-2-acrylamido-2-methyl propane sulfonic acid) as a polyanion with varying polyelectrolyte contents under different cross-linking conditions. Our method can prepare CM membranes of a large area easily at low manufacture cost. Although the flux of electrolytes through the membrane is less than that through a typical charge mosaic membrane such as Desalton (R) (Tosoh Co., Ltd.), which was prepared using micro-phase separation, the permselectivity for electrolytes through the CM membrane was more than 4 times higher than Desalton (R). These CM membranes have enough mechanical strength to form thin layer on a porous support membrane, thereby increasing the flux of electrolytes. (C) 2012 Elsevier B.V. All rights reserved.