A two_dimensional array of resonant absorptive and dispersive medium is proposed. The transmission,reflection and absorption spectra of optical field transmitting in the structure are calculated. The photonic band gap caused by resonance(PBG), similar as the case of one_dimensional active photonic crystal, is observed. It’s found that the resonance between the border of the Brillouin zone and the resonant center of the atom in the array is the key condition for the formation of the PBG. Further discussion is carried on the study of the dependence of transmission spectrum on the structure,the resonant center and the absorption linewidth of the atoms in the array.