A high-flat broadband optical frequency comb (OFC) signal generation scheme is proposed, and the mechanism and simulation analysis of the signal generation mechanism and method of high-flat and wideband electro-optical comb are carried out. In the simulation analysis, the dual-drive Mach-Zehnder modulator is used to generate the optical frequency comb signal, the phase modulator is used to further increase the number of comb lines, and finally the flatness is improved by jointly optimizing the drive signal power and DC bias voltage of the Mach-Zehnder modulator. The simulation results show that the scheme can generate a broadband comb signal with a bandwidth of 1.08 THz, with a tone-to-noise ratio of 60 dB and a flatness of 0.5 dB. The proposed scheme is applied to the optical carrier terahertz communication system, and the transmission performance of single-channel and multi-channel 16th-order quadrature amplitude modulation (16QAM) terahertz signals in the case of back-to-back (BTB) or 10 km optical fiber transmission is verified by simulation. The results show that the bit error rate in each of the above cases is lower than the threshold of forward error correction code.