Nitrogen-doped diamond films have been synthesized by EA-CVD （electron assisted chemical vapor deposition） technique. The quality and nitrogen impurity states of the diamond films are characterized by SEM, raman spectroscopy, XPS and EPR speclroscopy, respectively. The results show that the morphology changes from well-defined facets to cauliflower-like structures, the content of amorphous carbon increases and the quality drops with increasing the nitrogen flow rate. Furthermore, in the films, it can be observed that nitrogen impurity exists in the forms ofNs^0, [N-V]^0 and [N-V]^1. The contents of [N-V]^0 and [N-V]^-1 are lower when the nitrogen flow rate is relatively high, and the concentration of Ns^0 varies from 15 ppm to 483 ppm.
