A tunable multi-frequency optical millimeter-wave signals generator scheme based on optical carrier-suppressed modulation was proposed theoretically. Millimeter-wave signals with tunable frequency multiplication factor can be obtained through the beating of two sideband components of the optical carrier-suppressed signal which are selected by the uniform fiber Bragg grating based on acousto-optic tunable filter. What′s more, in order to avoid the time shift of code effect caused by the chromatic dispersion of the fiber, the baseband data signals are modulated on only one sideband component of the optical carrier-suppressed signal. To investigate the scheme, some simulations have been done. It turns out that optical millimeter-wave signals with frequency multiplication factors of 2, 6, 10, 14, 18 and 22 will be generated. The transmission performance of the downlink of the radio-over-fiber system are also evaluated. Under the situation that the frequency multiplication factor is 22, when the optical millimeter-wave signals modulated with none-return-to-zero data signals of 2 Gbit/s, the eye diagrams are still wide open after transmitting through the fiber of 50km. Meanwhile, the power penalty is only 0.4 dB. The results show that the system with well transmitting performance can meet the requirements of communication.