The invention relates to a comb spectrum generation device and a method based on a double spectrum line cyclic frequency shift mode. The device comprises a quadruplicated frequency system and a cyclic frequency shift loop, wherein the quadruplicated frequency system comprises a cascaded dual-electrode Mach-Zehnder modulator, a cosine microwave signal source, a phase shifter and the phase shifter; and the cyclic frequency shift loop comprises a 3dB coupler, a polarization controller (PC), the cascaded dual-electrode Mach-Zehnder modulator, the cosine microwave signal source, the phase shifter, the phase shifter, a semiconductor optical amplifier (SOA), an optical filter, an adjustable delay line, a direct-current bias power supply and an optical fiber which is random in length but short as much as possible. The method comprises the steps as follows: firstly, generating two flat spectrums with an interval of 12.5 GHz through the quadruplicated frequency system; secondly, transmitting the spectrums into the loop for cyclic frequency shift; thirdly, carrying out down-conversion on every two spectrum lines through the loop, circulating in sequence, and compensating power through the SOA; and lastly, filtering out 16 required flat spectrum lines through the optical filter.