An acid resistant thin film composite nanofiltration (NF) membrane (named TPT-TMC/PSf membrane) was fabricated using interfacial polymerization. A precursor of poly(s-triazine-amine), 1,3,5-(tris-piperazine)-triazine (TPT), was synthesized and interfacially polymerized with trimesoyl chloride (TMC) to fabricate NF membrane on the surface of a polysulfone (PSf) ultrafiltration membrane. The chemical structure, surface charge and morphology of the TPT-TMC/PSf membrane were characterized by attenuated total reflection Fourier transform infrared spectrometer (ATR-FTIR), zeta potential measurement, and scanning electron microscope (SEM), respectively. The results indicated that the TPT-TMC/PSf membrane has a thinner skin layer and a smoother and more negatively charged surface than the conventional polypiperazine amide NF membrane. The newly fabricated TPT-TMC/PSf membrane exhibited excellent rejections against different aqueous salt solutions [Na2SO4(98.6%) > MgSO4(97.0%) >NaCl (40.5%)]. The membrane also exhibited excellent acid resistant behavior. After being immersed in the 0.05 M H 2SO4 aqueous solution for 720 h, stable water permeance of about 8.68 L m(-2)h(-1) bar(-1)and MgSO4 rejection above 94.2% still achieved.