tively, and Fig. 4(c) and (d) display the total DOS of N$_{Bri}$ system and PDOS of N atom, respectively. In the total DOS, very narrow and sharp peak at the Fermi level is observed. We draw the PDOS of N atom and find the peak arises from from the N adsorption and the N atom is nearly 100% spin polarized. In the band structure, we find the very localized states at the Fermi level in the minority spin band structure. Such quasilocalized states give rise to the strong Stoner magnetism with magnetic moment of 0.65 µ B located at the N atom. In the PDOS of N atom, between the energy -0.5 eV and -1 eV, another narrow peak is obtained. Both in the majority and minority spin band structures, the corresponding flat impurity bands in the energy range from -0.5 eV to -1 eV are observed. In addition, both in the majority and minority band structures, the characteristic conical point at K point still can be clearly identified, implying the bilayer graphene is not strongly purturbed by the N atom. The critical difference is that, in freestanding graphene the Fermi level coincides with the conical point, while the Fermi level obtained in N-intercalated system is shifted down- ward and becomes below the conic point. A shift downwards (upwards) means the holes (electrons) are donated by the adsorption atom. The manganese doping (electron donor) results in the upward shift of the Fermi level, reported by previous investigations [9]. Band structure and density of states of O$_{Bri}$ system are displayed in Fig. 5, where Fig. 5(a), (b) and (c) are the band structure, total density of states, and partial density of states of O atom, respectively. The calculation shows the O$_{Bri}$ system is nonmagnetic. From the above analysis about N$_{Bri}$ and C$_{Hol}$ systems, we see the impurity states localized around the Fermi level play an important role in the magnetic properties, and the intercalated atom itself is spin-polarized. In O$_{Bri}$ system, we do not get such localized states around the Fermi level, and the O atom is nonmagnetic. In the PDOS of O atom, we find the peak nearest to the Fermi level is around the energy of 0.75 eV. From the band structure, we can also see that the impurity state nearest to the Fermi level is at the energy of 0.75 eV. Like N$_{Bri}$ system, the O$_{Bri}$ system also undergoes a change from semimetal to metal, because O atom get electrons form graphene, thus the Fermi level shifts downward. In summary, we calculated the structure, electronic and magnetic properties of the bilayer graphene with intercalated atoms C, N, and O by the ab - initio density function theory. Impurities even at very low density may bring fruitful physical properties for bilayer graphene system. Structure relaxation shows that the intercalated atom although initially positioned 6