ZnO nanofibers were fabricated by electrospinning. The samples were characterized by Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman technique. Field emission scanning electron microscopy (FE-SEM) shows that the obtained ZnO nanofibers were randomly aligned on the substrates. XRD and Raman patterns show that the ZnO nanofibers is the wurtzite structure. The turn on electric field of the ZnO nanofibers for generating a current density of 10 μA/cm2 is 14 V/μm and the current density is over 1 mA/cm2 at an applied field of about 18.9 V/mm. The corresponding Fowler-Nordheim plot shows a linear behavior. The possible emission mechanism is discussed.