In this study, it is presented a solvent addition method to significantly increase the performance of reverse osmosis (RO) membranes. Polyamide (PA) thin film composite RO membranes were prepared by interfacial polymerization (IP) method with a mixture containing dimethyl sulfoxide (DMSO) in different weight percent-ages. With the addition of DMSO, the selective PA layer was successfully activated, increasing its water flux to 41.7 L/m2 h while preserving a NaCl rejection of up to 95.7%. Morphological characteristics and properties of the model PA film under the influence of solvent with different weight percentages of DMSO showed the structural deformation caused by the activation of the PA layer, which affects the pore size and separation properties of the membrane. The research provides an expandable way to fabricate high-performance mem-branes in terms of flux and desalination with good resistance to fouling agents of polymeric membranes.