The embodiments of the present application disclose an optical comb based ROADM Add/Drop transceiving system, terminal and method, wherein the method includes: passing signals generated by an Add laser through an Add carrier apparatus to produce desired Add carrier signals; after selecting M channels of Add carrier signals according to Add management and control signaling, performing IQ modulation and carrier channel combination respectively, and transmitting the combined signal to a switching node and monitoring module; after the switching node and monitoring module outputs the combined signal, performing power splitting and transmitting signals to a coherent receiver; passing signals generated by a Drop laser through a Drop local oscillator apparatus to produce local oscillator signals, selecting N channels of local oscillator signals according to Drop management and control signaling, and transmitting the local oscillator signals to the coherent receiver; and after receiving the power split signals and the local oscillator signals, the coherent receiver performing demodulation, wherein M and N are numbers of channels of signals of an Add transmitting terminal and a Drop receiving terminal.