Membranes fouling and their degradation using free chlorine are the most common challenges in the desalination process. A blend nano-composite polysulfone /polyaniline were prepared as a substrate for the active polyamide layer. In this work, nano polyaniline emeraldine salt was prepared using a simple chemical oxidative polymerization method. It was added to the polysulfone (PS) substrate layer in the presence of sodium lauryl sulfate as a hydrophilic agent to enhance reverse osmosis properties of the thin film composite membrane. Unmodified and modified polyaniline nano-particles membranes were characterized using XRD, EDX, FT-IR, SEM, particle size distribution and contact angle. The membranes performance was evaluated in terms of water flux and salt rejection using a cross-flow filtration unit. The results showed that the nano-composite membrane had much better water permeability (66 L/m²/h) compared to the control membrane (57 L/m² /h) without significant change in the percentage of salt rejection. The resistance of membranes to bio-fouling and chlorine degradation was evaluated using bovine serum albumin (BSA) as fouling model and sodium hypochlorite, respectively. The modified membrane was more resistant to bio-fouling and chlorine attack because of the strong electrostatic repulsion between poly-aniline PANI and BSA. The prepared polysulfone -polyaniline nano-composite substrate has been enhanced the performance of thin film composite as a reverse osmosis membrane.