Proposes a radio-over-fiber system through MIZ generating optical mm-wave. The system applies the mixed-frequency signals with base-band signals and LO signals to drive an optical phase modulator for generating multiple sidebands optical signal. Uses MZI to increase the optical signal with double frequency. Establishes the theoretical model for producing optical mm-wave and verifies the feasibility of the system through simulation test. The result shows that the 2.5 Gb/s base-band signal modulated by 40GHz optical mm-wave is visible on eye diagram after 60 km fiber transmission with 4.2dB power penalty.