Nitrogen was implanted into the chemical vapor deposition(CVD) diamond films, and the electron fieldemission properties of the nitrogenated diamond films were investigated. Raman and xray photoelectron spectroscopy(XPS) measurement revealed that nitrogenimplantation damaged the structure of diamond film and promoted the formations of sp2 C—C and sp2 C—N bonding. By increasing the implantation dose， the threshold field of the emission of the diamond film could be lowered from 18V/μm to 4V/μm. The enhancement of field emission for nitrogenimplanted CVD diamond films was attributed to the increase of the fraction of sp2 C bonds and the formation of defect bands within the bulk diamond band gap induced by nitrogenimplantation, which could alter the work function and elevate the Feimi level. Consequently, the energy barrier on diamond surface for electron tunneling was reduced.