We theoretically investigate the magnetic-field-induced terahertz absorption enhancement of a graphene-based one-dimensional photonic crystal using the 4×4 transfer matrix method for the circular polarization of light. The results show that the magnetically tunable absorption of the structure depends on the circular polarization state, magnetic circular dichroism, and, interestingly, absorption behaviors of right-handed and left-handed circularly polarized light interchange by changing the direction of the magnetic field. These properties can be used to design the circular-polarization-based sensors.