The amplification effect on stimulated Brillouin scattering (SBS) and Rayleigh scattering in the backward pumped G652 fiber Raman amplifier (FRA) is studied. The pump source is a 1427.2-nm fiber Raman laser whose power is tunable between 0-1200 mW, and the signal source is a tunable narrow spectral bandwidth (<10 MHz) external cavity laser (ECL). The Rayleigh scattering lines are amplified by the FRA and Stokes SBS lines are amplified by the FRA and the fiber Brillouin amplifier. The total gain of SBS lines is the production of the gain of Raman amplifier and that of Brillouin amplifier. In experiment, the SBS gain is about 42 dB and the saturation gain of 25-km G652 backward FRA is about 25 dB, so the gain of fiber Brillouin amplifier is about 17 dB.