Polyurethane (PU) was synthesized from polypropylene glycol (PPG 2000) and diphenylmethane diisocyanate (MDI-50) by a prepolymerization method.The carbon nanotubes(CNT) were added in the prepolymerization process to synthesize carbon nanotubes / polyurethane (CNT / PU),while carbon black(CB) was added in the process of chain extension to synthesize carbon black / polyurethane (CB / PU).CNT/PU nanofibers and CB/PU nanofibers were obtained by eletrospinning technique.The structure and properties of the two kinds of nanofibers were characterized by SEM,TEM,FTIR,DSC,XRD , electrical,mechanical and sensing properties tests.The results showed that, because of the selective embedding of carbon nanotubes / carbon black in the soft and hard segments of PU,the degree of microphase separation of PU nanofibers increases / decreases;the elongation at break of CNT / PU fibers decreases, and the breaking strength of CB / PU fibers increases.The content of conductive filler is based on the mass of polyurethane (the total mass of PPG 2000, MDI-50 and anhydrous ethylenediamine used in the experiment)，when the CNT content is 6%, the resistivity of CNT / PU fibers was 1.22Ώ•m and the strain sensing coefficient (GF) was 45.64; when the CB content is 12.5%, the resistivity of CB / PU fibers was 0.14Ώ•m, GF was 167.43.