In this paper, calculating model of Subcarrier Multiplexing (SCM) Radio over Fiber system using Coherent Receiver is built. Basing on it, we investigate dominant noises, determine signal power, calculate signal-to-noise ratio at receiver and receiver sensitivity with considering influence of subcarriers on system signal. Next, we simulate system by matLab, draw graphs showing receiver sensitivity versus number of subcarriers, versus EDFA gain, vesus local oscillator power in Coherence receiver corresponding to different modulations such as ASK, BPSK và QPSK. Besides, we also compare performance of two systems-using Direct Detection (DD) and Coherence Detection. Basing on comparing, analyzing, evaluating the performance of two these systems, we find out that thanks to using Coherent receiver, sensitivity is improved and signal quality transfered in this system is enhanced remarkably.