The influence of formation temperature on the ultradrawing properties of ultrahigh-molecular-weight polyethylene/carbon nanotube (UHMWPE/CNT) fiber specimens is investigated. Gel solutions of UHMWPE/CNT with various CNT contents were gel-spun at the optimum concentration and temperature but were cooled at varying formation temperatures in order to improve the ultradrawing and tensile properties of the UHMWPE/CNT composite fibers. The achievable draw ratio (Dra) values of UHMWPE/CNT as-prepared fibers reach a maximum when they are prepared with the optimum CNT content and formation temperature. The Dra value of UHMWPE/CNT as-prepared fibers produced using the optimum CNT content and formation temperature is about 33% higher than that of UHMWPE as-prepared fibers produced using the optimum concentration and formation temperature. The percentage crystallinity (Wc) and melting temperature (Tm) of UHMWPE/CNT as-prepared fiber specimens increase significantly as the formation temperature increases. In contrast, Wc increases but Tm decreases significantly as the CNT content increases. Dynamic mechanical analysis of UHMWPE and UHMWPE/CNT fiber specimens exhibits particularly high α-transition and low β-transition, wherein the peak temperatures of α-transition and β-transition increase dramatically as the formation temperature increases and/or CNT content decreases. In order to understand these interesting drawing, thermal and dynamic mechanical properties of the UHMWPE and UHMWPE/CNT as-prepared fiber specimens, birefringence, morphological and tensile studies of as-prepared and drawn fibers were carried out. Possible mechanisms accounting for these interesting properties are proposed.