The cascaded stimulated Brillouin scattering(SBS) on S-band forward pumped and backward pumped distributed fiber Raman amplifier(FRA) was studied.Forward SBS is observed during pump power is larger than the threshold value of SBS in a S-band FRA and signal source is a tunable narrow spectral bandwidth (<100 MHz) LD.Cascaded multi-order SBS is observed in the Stokes region during the pump power increases.The power of even order SBS is stronger than odd order Brillouin-Rayleigh scatterng in the experiment.The gain is down and noise increases during the pump power continuesly increases.FRA can not be used on DWDM transmit system because of the crosstalk of cascade SBS.So we must control pump power on FRA and incident signal power in fiber.Companion lines on two sides of amplified signal light and SBS is observed on S-band FRA.