The photonic crystal filter and optical switch are designed based on the garnet-type ferrite magnetic material. The band structure of the photonic crystal with a specific radius is analyzed by the plane wave expansion method (PWM), and the change of coupling frequency of magnetic materials with the magnetic field is analyzed by the finite-difference time-domain (FDTD) method. The results show that, when the magnetic field is not added, this device has excellent frequency selection and filtering functions, the transmissivity of each target light signal is above 90% and the channel crosstalk is small. After the addition of the magnetic field, the coupling frequency of the coupling cavity changes and the device is in a closed state. The maximum stable closing time of this device is 26.4 ps and the maximum transmissivity is only 8%, which indicates that the cut-off effect is obvious and it possesses a good switching characteristic.