High-strength poly(ethylene terephthalate) (PET) fibers were obtained using low molecular weight (LMW) polymervia horizontal isothermal bath (hIB), followed by postdrawing process. We investigated the unique formations of different precursors, which differentiated in its molecular orientation and crystalline structures from traditional high-speed spinning PET fibers. Sharp increase in crystallinity was observed after drawing process even though the fibers showed almost no any crystallinity before the drawing. Properties of as-spun and drawn hIB and control filaments at different process conditions were compared. As would be expected, performances of resulted treated undrawn and drawn fibers have dramatically improved with developing unique morphologies. Tenacities more than 8 g/d for as-spun and 10 g/d for drawn treated fibers after just drawn at 1.279 draw ratio were observed. These performances are considerably higher than that of control fibers. An explanation of structural development of high-strength fibers using LMW polymer spun with hIB is proposed. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42747.