Hollow-fiber membranes were prepared by dry-wet spinning under different spinning conditions. The used spinneret was tube-in-orfice type and the membrane material was polysulfone (Udel P-3500). N-methyl-2-pyrrolidinone (NMP) and water were used as solvent and coagulant, respectively The concentration of the dope solution was 22 wt %. The effects of the three spinning factors-spinning height; extrusion rates of dope solution and inner coagulant; dimensions (inner diameter, outer diameter, and thickness) and permeation properties of the hollow-fiber membranes-were studied. The results were as follows : With changes in the spinning factors, spinning velocity and falling time before the membrane entered the water (coagulant) were changed; consequently, the structures and the dimensions of the hollow-fiber membranes varied with a certain tendency. The permeation properties of the hollow fibers were related very closely to the changes in the fibers’ structures and dimensions.