In order to suppress the third-order intermodulation distortion of the down converting Radio-over-fiber (ROF) link, linearized down converting ROF link based on a Polarization Modulator (PolM) in a Sagnac loop is proposed. First, the modulation method and the principle of this technique are described theoretically. And then, simulation analysis about ROF link based on the technology is carried out. The analysis results show that the technology can get optimized link gain, and spurious free dynamic range reach 127.4 dB.Hz2/3 by optimizing the parameters of the three Polarization Controllers (PCs) and the polarization angle between the polarizer and the spindle of PBS.