pH- and thermo-sensitive polyethersulfone (PES) hollow fiber membranes were prepared for the first time by blending a terpolymer of poly(N-isopropylacrylamide-co-methacrylic acid-co-methyl methacrylate) (P(NIPAAm-MAA-MMA)) via dry-wet spinning technique based on a liquid-liquid phase separation. The terpolymer was synthesized via free radical solution polymerization. Scanning electron microscopy (SEM) results indicated that the membrane morphology had been altered after the introduction of the terpolymer. The modified PES hollow fiber membranes showed pH-sensitivity, and the pH-valve effect was observed at the pH value between 7.0 and 10.0; the modified PES membranes also showed thermo-sensitivity, the hydrodynamic permeability changed slightly while the pore sizes changed significantly when the temperature increased, which indicated that the modified membranes could be used for thermo-sensitivity separation, but not suitable for thermo-sensitivity hydrodynamic permeability control. The membranes also showed excellent pH- and thermo-reversibilities. (C) 2012 Elsevier B.V. All rights reserved.