In this study, three types of conjugate fibers, sea-islands type, orange split type, and side by side type, were prepared by using an on-line steaming process through a high-speed spinning technique in order to improve the processibility, efficiency, and properties of the fibers. It was found that the weight reduction ratios of orange split and sea-island polyester/copolyester fibers were higher than that of polyester fibers. The SEM results indicate that the split time was shortened by using the ultra-high-speed melt spinning process. The nozzle-draft increased and elongation decreased for side by side conjugate fibers after the spin speed was increased. The elasticity and crimp ratio of side by side conjugate fibers were significantly affected by the drawing temperature. POLYM. ENG. SCI., 2012. (C) 2011 Society of Plastics Engineers