The time evolution of the quantum entropy in a GaAs/AlAs one-dimensional photonic crystal (1DPC) with an atomic system defect layer is investigated in this work. The entanglement between atomic system and their spontaneous emission fields near the edge of the photonic band gap (PBG) is coherently controlled by the coupling field. Comparison between the atom-photon entanglement of the atomic system in the vacuum surrounding and that near the PBG of the 1DPC shows that the degree of entanglement strongly depends on the PBG. We find that degree of entanglement is strongly dependent on the intensity and detuning of the coupling and probe fields. Furthermore, the effect of the phase difference between applied fields on the atom-photon entanglement is studied. The potentially possible technological applications can be provided by the proposed model in the quantum optics and quantum communications based on photonic crystal.