Polyurethanes (PUs) of a suitable molar ratio of monomers were found to have shape-memory behavior. In this study, four series of PUs were synthesized by 4,4＇-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BD), and various molecular weights of poly( tetramethylene oxide)glycol (PTMO) to study the influence of the soft segment (PTMO) on the shape-memory behavior of PUs. The investigation on thermal and dynamic mechanical properties was performed using DSC and DMA; then, the morphology of the PUs was directly observed by TEM. At the range of the individual glass transition, a similar recovering behavior was found from the deformed specimen that contained the same composition but different molecular weights of PTMO. However, the phase separation between the soft and the hard segments of the PUs would influence their shape-memory behavior. On the other hand, a large number of the dispersed phase of the PUs would delay the recovery rate of the deformed specimens using a high molecular weight PTMO.