L-cysteine as an amino acid was used for the modification of glycidyl POSS in the synthesis of L-cysteine functionalized POSS, including carboxyl, hydroxyl, and diamine groups. Then, the synthesized nanoparticles were applied to fabrication of L-cysteine POSS-TiO2 composite nanoparticles. NF membranes were prepared from the incorporation of different concentrations of the synthesized composite nanoparticles into the polyether-imide (PEI) as the membrane matrix. The prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and atomic force microscope (AFM). Moreover, the separation performance of the NF membranes was examined by pure water flux (PWF) and the separation of Na2SO4, Pb(NO3)2, Cr(NO3)2 and Cu(NO3)2 aqueous solutions. The results showed the increase of pure water flux due to present hydrophilic groups on the membrane surface. The highest pure water flux obtained was 22.03 L/m2h in 1 wt% of nanoparticles. Furthermore, the rejection of Na2SO4 and Pb(NO3)2, CrSO4, and Cu(NO3)2 improved to 78%, 64%, 67% and 66% that increased 11%, 33%, and 22%, and 39% compared with the pristine PEI membrane, respectively. Finally, the best FRR% (81%) was obtained for 0.1 wt% of the composite nanoparticles (M3).