Capacitive deionization (CDI) has been attracted great mterest as an emerging desalination technology and the electrode materials play a critical role on improving CDI performance. In this work, nitrogen-enriched activated carbon fibers (AN-CFs) were prepared from the natural based silk cocoon through simple carbonization and CO(2)activation. Their electrochemical and electrosorption behaviors were studied in NaCl solution. The results show that AN-CFs exhibit a fibri form porous structure with rich nitrogen element and CO(2)activation enhances their specific surface area. Compared with unactivated nitrogen-enriched carbon fibers (196.05 F g (-1) at 1 mV s(-1)12.02 mg g(-1) in 1000 mg l(-1) NaCl solution), AN-CFs exhibit more excellent capacitive (236.03 F g (-x)) and CDI (16.56mg g(-1)) performances, showing that CO2 activation is proved to be an effective method to improve electrochemical and electrosorption performances and the AN-CFs should be a promising electrode material for CDI application.