We proposed a theoretical model of magnetron photonic switching circuit (MPSC) in photonic crystal (PC) and investigated the properties of MPSC using the plane wave expansion method in combination with supercell method. This model is a PC composed of dielectric pillars set in air, in which one row of dielectric pillars is replaced by ferrite material with the dielectric constant same as that of the original dielectric pillars. When external static magnetic field is applied, the permeability of the ferrite pillars will not be equal to one and guide modes along the row of ferrite pillars may be generated in band gap. When the external field is removed, this system reverts to a perfect PC. Thus, this system forms a photonic switching circuit controlled by the external field. In calculation, we take square pillars set in square lattice. The calculation results show that this MPSC is reasonable and realizable, and some valuable results are obtained.