Aiming at the problem of the application of the integrated photonic filter in the 3～5 μm atmospheric window banda mid-infrared add-drop filter based on the apodized grating-assisted contra-directional coupler (contra-DC) is studied and designed. The complementary lateral-misalignment method is used for phase modulation to achieve spectral sidelobe suppression and eliminate spectral distortion and broadening caused by the conventional lateral-misalignment modulation method. Simulation results show that the device can achieve a high Sidelobe Suppression Ratio (SLSR) of 22 dB, bandpass filter spectrum is flat at the top and the filtering spectrum is close to the box shape. The device has low insertion loss of about 0.4 dB through port and 0.45 dB drop port.