The scheme of generating optical frequency combs by cascading M-Z modulator (MZM) and phase modulator (PM) is researched, and an optical fiber link is built on the theoretical basis for experimental verification, which can produce optical frequency combs with a signal-to-noise ratio of about 35 dBm, a flatness of 4.5 dBm and about 22 comb teeth at most. The feasibility of the scheme is verified by researching on the change of spectrogram at different frequencies and powers in experiments.