This paper presents a photonic crystal ring cavity-based Optical Add/Drop Multiplexers（OADM）.In a square lattice photonic crystal structure

this device implements optical add/drop multiplexing by the coupling of line defects with ring cavity and the upload/download of the light waves at the specific frequency using the frequency selection function of the ring cavity.The simulation results show that when the incident port has incident light waves at multiple wavelengths

this OADM can upload/download light waves at a wavelength of 1 554.9 nm

the upload/download rate is 98.23%

the insertion loss is0.077 55 dB and the channel isolation is 33.37 dB and 32.98 dB respectively.With excellent performances

this device has reference significance to the development of integrated devices for optical communication.