The coherent Rayleigh noise (CRN) induced by Rayleigh backscattered (RB) light and backward transferred light in the fiber is a main noise source in bidirectional communication systems.In this paper,the bidirectional communication system with a single mode fiber for 10 GHz analog radio frequency (RF) signal is set up,and the orthogonal polarization method for reducing CRN is proposed.Orthogonal polarization communication is achieved by a polarization rotator.The system performance is analyzed by simulation.The simulation results show that CRN of the bidirectional communication system can be diminished by using the method and RB light would decrease by an order of magnitude.Signal to noise ratio (SNR) of the system would increase by 15-fold.The orthogonal polarization method has the advantage of easily adjusting for polarization rotation angle.