Power coupled equations for a multi-wavelength broadband Raman amplifier (MBRA) are reasonably simplified.A multi-step average power method is used to compute composite Raman gain of multi-signal in a dense wavelength division multiplexed system (DWDM).A conventional simulated annealing algorithm is applied for optimization of MBRA.A simple object function is proposed considering the gain bandwidth,on-off gain,gain flatness and other characteristic parameters.Influences of the number of pump,input power and wavelength distribution on Raman gain are studied.Relations among gain bandwidth,on-off gain,gain flatness and the number of pump of MBRA are revealed.Simulation shows that the optimal signal bandwidth Δλ becomes boarder with the increasing of the number of pump and narrower with the increasing of Raman gain and the improvement of flatness.