Core-shell structured PEO-chitosan nanofibers have been produced from electric field inducing phase separation. Chitosan, a positive charged polymer, was dissolved in 50 wt % aqueous acetic acid and the amino group on polycation would protonize, which would endow chitosan electrical properties. Chitosan molecules would move along the direction of the electric field under the electrostatic force and formed the shell layer of nanofibers. Preparation process of core-shell structure is quite simple and efficient without any posttreatment. The core-shell structure and existence of chitosan on the shell layer were confirmed before and after posttreatment by TEM and further supported by SEM, FTIR, XRD, DSC, and XPS studies. Blending ratio of PEO and chitosan, molecular weight of chitosan for the mobility of chitosan are thought to be the key influence factors on formation of coreshell structure. Drug release studies show that the prepared core-shell structure nanofibers has a potential application in the biomedical fields involving drug delivery. (C) 2015 Wiley Periodicals, Inc.