Currently, the polyamide (PA) membranes by reverse osmosis (RO) are highly effective in their applications for water desalination and water reuse. However, they offer poor resistance to strong oxidants such as chlorine, resulting in chain deformation. In this work, we have studied the RO performance of membranes, which were made from a copolymer of two different aromatic polyamide (poly-terephtalamide diphenyl sulphone (PTDS) and poly-isophtalamide diphenyl sulphone (PIDS)) by using the phase-inversion method. The membranes were tested before and after treatment with a sodium hypochlorite solution. The results showed a remarkable tolerance of these membranes to a chloration test.