In this paper, a coherent balance detection method is proposed to suppress the noise of ROF link output signal. By introducing local oscillator light to couple with signal light, the output light suppresses the direct current disturbance of the optical signal through a subtractor, thereby suppressing RIN, indirectly suppressing the noise of the output signal and improving the signal-to-noise ratio of the output signal. Optiisystem simulation shows that when the RIN of signal light is higher than the RIN of local oscillator, the higher the power of signal light, the better the improvement effect of output signal noise of coherent balance detection system. At this time, if the power of local oscillator is higher than that of signal light, the signal-to-noise ratio of output signal of coherent balance detection will be improved. When the frequency difference between lasers is 0.1 GHz, the signal-to-noise ratio of coherent balance detection output signal will be improved. Compared with the traditional feedback method, the balanced detector can effectively reduce the access of external electrical signals. The best working area and environment of balanced detection method to suppress roF links is summarized, which provides an experimental reference for the subsequent research and improvement of this method.