In order to further improve the performance index of second-order Raman fiber amplifier, the main parameters of second-order RFA were analyzed. First, a structural model that can be controlled by optical switches and switched between two modes of traditional second-order and traditional first-order RFA is designed. It is proved through simulation that second-order RFA can increase the system gain and improve noise performance. The gain performance of first-order RFA is optimized. The optimization goal is to reduce the flatness. The particle swarm optimization algorithm is used to optimize the configuration of the wavelength and power of the pump light. After further structural improvement, a second-order RFA with a gain of 24.50 dB and a gain flatness of 0.98 dB were achieved in a 100 nm bandwidth. These results provide a reference for the design of second-order RFA with better performance in the future.