In this study, we demonstrated that poly(ether sulfone) (PES) hollow fiber membranes with almost defect-free surfaces could be prepared at low PES concentrations if the hollow fibers were spun at low temperatures by dry-jet wet spinning. A series of hollow fiber membranes were spun at different coagulation batch temperatures (T-c) and dope solution temperatures (T-d). Effects of T-c and T-d on the membranes' morphologies and gas separation performances were investigated. Membrane morphologies characterized by using a scanning electron microscope (SEM) showed that the skin layer thicknesses increased with the decreases in T-c and T-d. Moreover, mean surface pore sizes of the membranes, which were evaluated by using the gas permeation method, significantly decreased as T-c or T-d decreased. PES hollow fiber membranes spun at the lowest temperatures (T-c = 7 degrees C, T-d = 3 degrees C) showed O-2 and CO2 permeances of 18.9 and 53.5 GPU, respectively. And selectivities of O-2/N-2, CO2/N-2, and CO2/CH4 gas pairs were 1.15, 3.26, and 1.24, respectively. After silicone coating, the selectivities increased to 7.24, 47.7, and 39.4, respectively, but O-2 and CO2 permeances decreased to 4.85 and 31.9 GPU, respectively. To our best knowledge, the gas separation performance was the test among all PES hollow fiber membranes.