The invention discloses a polarization multiplexing millimeter-wave radio-over-fiber (RoF) system with a high frequency spectrum utilization rate and relates to the field of RoF. By the system, the problems of low frequency band utilization rate, high noise and high bit error rate of the conventional RoF system are solved. In the system, a double-electrode Zehnder modulator is connected with inputs of a first laser, a radio frequency signal generator, a Pi phase shifter, a bias voltage source, the ground and a first 3dB coupler respectively; one output of the first 3dB coupler is connected with an emitting antenna through a first polarizer, a first strength modulator, a second 3dB coupler, an er-doped fiber amplifier (EDFA), a down link optical fiber, a third 3dB coupler, a first analyzer, a first photoelectric converter, a first filter and a millimeter-wave amplifier; and the other output of the first 3dB coupler is connected with a receiving antenna through a second analyzer, a second 3dB coupler, the EDFA, the down link optical fiber, a second photoelectric converter, a second filter and a multiplier. The polarization multiplexing millimeter-wave RoF system is mainly used for RoF systems with high frequency band utilization rate, low noise and low bit error rate.