In this work, nanofiltration (NF) membranes doped with ZnO nanoparticles (NP's) were prepared via interfacial polymerization reaction (PI). ZnO nanoparticles were added during PI reaction in different ways: by adding in organic solution, in aqueous solution and in both solutions. PI reaction was determined by FT-IR analysis and the NF membranes prepared by these methodology were characterized by measuring the permeability, water angle contact, molecular weight cut-off, thermogravimetric analysis, scanning electronic microscopy and zeta potential, so for removal of Na2SO4, NaCl and MgSO4, (at 1000, 3000 and 5000 mg L-1). According to the results, the doping of membranes increases the removal of salts, reaching up to 97.8%. The salt removal order was Na2SO4 >MgSO4 >NaCl. NP's incorporating in the polymer film depends on the way they are added, gettinE, a higher dopant when added in both monomers. According to the SEM micrographs of the membranes prepared with NP's in the organic phase, show a NY's exposed surface, which affects their performance.