A novel method based on PSO is developed to design the countermultiwavepumped broadband fiber Raman amplifiers. By using PSO,the 12 variables of 6 pump laser′s pumped wavelength and pumped power simultaneously and efficiently were optimized.Then according as the pumpedpower′s evolution, the PSO′s low precision was overcome better. Finally, a FRA with the gain ripple less than 0.6 dB in 100nm gain spectra is obtained.This paper gives a feasible method for designing the ultrabroadband FRA.