In this paper, we theoretically investigate the transmittance characteristics of one-dimensional defective photonic crystal in microwave radiations based on the fundamentals of the characteristic matrix method. Here, the defect layer is magnetized plasma. The numerical results show the appearance of defect peaks inside the Photonic Band Gap. The external magnetic field has a significant effect on the permittivity of the defect layer. Therefore, the position and intensity of the defect peak are strongly affected by the external magnetic field. Moreover, we have investigated the different parameters on the defect peaks as the plasma density, the thickness of the plasma layer and the angle of incidence. Wherefore, the proposed structure could be the cornerstone for many applications in microwave regions such as narrowband filters.