Nitrogen- and Boron-doped Nanocrystalline Diamond (NCD) Thin Films were deposited on silicon substrate using a Microwave plasma-enhanced chemical vapor deposition (MPECVD) method. X-ray absorption near-edge structure (XANES), measurements have been performed chemical structure and bonding configuration for a variety of Nitrogen- doped、Boron-doped and undoped Nanocrystalline diamond Thin films. We find that sp2 and sp3 in microcrystalline diamond series and Nanocrystalline diamond series are different, when the grain size is reducing. The phenomenon is corresponding to the field emission properties. We suggest that doping in MCD and NCD have different mechanism. We will discuss in this paper.