In order to improve radio over fiber (RoF) system performance and reduce system complexity, a novel RoF system scheme with continuously tunable optical carrier-to-sideband ratio (OCSR) was proposed. Using polarization multiplexing technology, the OCSR can be tuned from –36 dB to 26 dB by adjusting a polarization controller (PC). The effects of polarization angle of PC, modulation index and extinction ratio on OCSR were studied by theoretical analysis and experimental simulation, in which the results of theoretical calculation and experimental simulation are in good agreement. It is found that the receiver sensitivity can be improved 7.8 dB by tuning the OCSR from 10.41 dB to 0 dB. The power penalty is 0.07 dB for the 0 dB OCSR after 40 km transmission, which means the impact from the fiber link can be ignored.