In this paper,a novel scheme for optical single side-band signal gen eration based on multi-frequency modulation is proposed.When a modulation signal containing fu ndamental frequency and harmonic waves was loaded onto a Mach-Zehnder electro-optic modu lator,most of the optical power would concentrate on one sideband,while other frequency component s were suppressed, and made a single sideband signal.As an example,the signal spectrum generate d by 10-tones phase modulation was numerically calculated.Energy efficiency up to 88%,carrier su ppression ratio of 24dB and sideband suppression ratio of 18dB were obtained in our simulation,w hich indicates that the proposed scheme is feasible and efficient.Further simulation results show t hat the energy efficiency,carrier suppression ratio and the sideband suppression ratio all rise with the increase of the number of harmonic waves. Thus it can be seen that to get optical single sideband signal with high quility,as many modulation frequencies as possible should be used if the ex periment condition satisfied.Commercial Mach-Zehnder electro-optic mudulator and RF driver were used in our scheme,wh ich makes the virtue of high energy efficiency and simple configuration for operation.It prov ides an effective way to generate an OSSB signal for optical communication or optical sensing systems.