Abstract: Power propagation equations of multi-pumped fiber Raman amplifiers(FRA)are reasonably simplified,a mathematical model of composite Raman gain of multi-signals in dense wavelength division multiplexed system(DWDM)amplified by multi-pumped FRA is built,and the influence of stimulated Raman scattering(SRS)on Raman gain is analyzed.Based on such a simple and effective model,an algorithm to optimize pump wavelength distribution and input power is introduced and the ultra broad and flat Raman gain spectra are implemented.All the simulation and analyses supply valuable references for the application of multi-pumped FRA in DWDM system.