In order to increase the output bandwidth of Raman fiber amplifier(RFA) and reduce the gain flatness. The relationship between the gain characteristics and the pump source under different parameter settings is analyzed by using OptiSystem software. The pump power, pump wavelength, fiber length and effective area are optimized and simulated. The simulation results show that the proposed optimization method can maximize the gain of RFA within the set range, and obtain better gain flatness by changing the relevant parameters.