A scheme to generate a tunable optical frequency comb (OFC) based on coupled radio frequency (RF) signals and Mach-Zehnder modulator (MZM) is proposed. The coupled RF signal generated using a cheap signal source can be used to replace the expensive and high-frequency signal sources, thereby reducing the cost of OFC generators. The theoretical model of OFC generated using various coupled RF signals is established, and the scheme is verified using OptiSystem 13.0. The effects of the modulating voltages of upper and lower arms of MZM, output frequency of the RF signal source, and coupling mode on the comb number, power flatness, and frequency interval are analyzed. Simulation results indicate that for 5-GHz output RF signal and 4 times multiplicative-couple, OFC with frequency interval of 10 GHz, comb line number of 7, and power flatness of 1.88 dB can be obtained. Moreover, the proposed scheme can generate OFC with additional comb-lines, better flatness, and lower cost compared with the same frequency interval OFC generation scheme based on a single MZM. The proposed scheme provides guiding significance for the design of low-cost and high-performance OFC generators.