The distributed fiber Raman amplifier (DFRA) is more and more attractive for its particular virtues such as in-line,wideband and low noise etc. Because of the virtues of in-line and low noise,DFRA is used as the in-line amplifier in long-distance fiber optic hydrophone (FOH) and to measure the change of noise. The experimental results show that the increases of intensity noise and phase noise are below 2 dB. Meanwhile,compared with erbium doped fiber amplifier (EDFA),DFRA has better performances when it is used as the in-line amplifier in the remote FOH system. So DFRA can be used as the in-line amplifier in long-distance FOH.