In this research mixed matrix PVC based-co-clay nanoparticles heterogeneous cation exchange membranes were prepared by solution casting technique. The effect of clay nanoparticles concentration in the casting solution on membrane electrochemical properties was studied. Scanning optical microscopy (SOM) images showed uniform particles distribution and relatively uniform surfaces for the prepared membranes. The membrane water content was improved initially by an increase of additive content ratio up to 1%wt in casting solution and then it began to decrease by more additive concentration. Moreover, swelling was measured less than 5% in thickness and negligible in length and width for the prepared membranes. Membrane potential, transport number and permselectivity were improved by increase of nanoparticles loading ratio. Utilizing Cloisite nanoparticles up to 1%wt in the casting solution also led to an increase in permeability and flux for prepared membranes. The ionic permeability and flux were decreased again by a further increase in additive concentration from 1 to 4%wt. Also, membranes exhibited lower permeability and flux for bivalent ions in comparison with monovalent type. The membrane E-conductivity and mechanical strength was enhanced by an increase of nanoparticles concentration in membrane matrix. The modified membrane containing 1%wt clay nanoparticles showed more suitable electrochemical properties compared to others.