Alternating layer-by-layer (LbL) deposition of polycations and polyanions on porous substrates is a convenient and versatile method for forming high-flux nanofiltration (NF) membranes. In this work, positively charged NF membranes were fabricated by the LbL assembly of poly(ethyleneimine) (PEI) and poly(sodium 4-styrenesulfonate) (PSS) on the modified polyacrylonitrile ultra-filtration substrate. The charge variation with each layer was characterized by zeta potential. ATR-FTIR, SEM, N2 adsorption and the weight changes with bi-layers were used to confirm the LbL deposition of the polyelectrolytes. NF performances of the prepared membrane with a number of bi-layers as well as solute concentrations were also investigated. The results of zeta potential showed that the whole multilayer films exhibited periodic variations in positive charge. NF results indicated that the rejection of Ni2+ and Cd2+ ions increased, while the permeate fluxes decreased with the number of bi-layers. And the rejections of the metal ion solutes were 98.02% for CuSO4, 95.53% for ZnSO4, 95.66% for NiCl2, 94.9% for CdCl2, along with permeation fluxes of 19.02, 19.72, 24.02, and 21.19 L/m2·h, respectively.