Abstract: Multi-walled carbon nanotubes (MWCNTs) reinforced poly(ε-caprolactone) (PCL) ult rafine composite fibers were prepared by means of elect rospinning. Scanning electron microscopy (SEM) , transmission electron microscopy (TEM), Raman spect roscopy, differential scanning calorimeter (DSC) and X-ray diff raction (XRD) were used to characterize the electrospun ultrafine MWCNTs/PCL fibers and the mechanical properties of fibers were also tested. The results indicate that MWCNTs have been dispersed in PCL, which can reduce the crystallization of PCL. When the content of MWCNTs is 0. 5 wt% , elect rospun MWCNTs/PCL composite fibers have the best mechanical properties with the lowest crystallinity of PCL.