We design a tunable parity-time (PT) symmetric structure, in which magnetic microcavity is inserted. By transmission spectrum calculated by the transfer matrix method,we research the modulation effects of microcavity resonance under the applied magnetic field on PT symmetric structure. An enhanced non-reciprocal band-edge mode is obtained, which can be modulated by directions and sizes of incident angles. The modulation transforms the band-edge modes between the left and right edges of the band. Results reveal that the increase of the magnetic field causes the edge mode to move to high frequencies, and the change of magnetic field direction also causes the transformation of the band-edge modes between the left and right band edges.