Polyacrylonitrile (PAN) is a favored material for electrospinning and also has been used successfully as a raw material of carbon nanofiber due to its useful and stable structure after treating adequate energy. The PAN nanofibers were prepared and irradiated by electron beam with different dose levels in order to confirm the most efficient dose level on nanofibers. The object of this work is to identify the stabilization of PAN during the irradiation and the effect caused from electron beam irradiation on PAN nanofiber sheets. Upon irradiation, the diameter of nanofibers decreased and the surface area accordingly increased. From structural analyses, that the degree of stabilization increases up to 2000 kGy by disruption C N group on PAN. Only short irradiation time less than 1 min can cause the stabilization effect that can be obtained from time-consuming thermal stabilization process.