Thin film composite (TFC) co-polyamide membranes were prepared by interfacially polymerizing secondary amide and highly hydrophilic aromatic primary amide (3,5-diaminobenzoic acid, BA). The salt rejection and flux of these membranes were measured at various feed pressures. Incorporation of the BA cause an increase in pure water permeability constant (A) and solute transport parameter (D-AM/kdelta). The rejection ability of NaCl and Na2SO4 dropped at a higher ratio of BA and piperazine (PIP). Membrane with a higher content of BA produced a loose-and defected skin layer. The reaction among the BA, PIP and trimesoyl chloride was further confirmed using Fourier transform infrared.