A novel method was proposed to optimize Raman/EDFA hybrid amplifiers based on an improved simulated annealing algorithm (ISAA) in this paper,and a simple object function was achieved according to power-coupled equations of erbium doped fiber Amplifier (EDFA) and fiber Raman Amplifier (FRA). The proposed ISAA can effectively solve the multimodal optimization including both global and local optima in the hybrid amplifier. Optimization results show that,under the conditions of the ON-OFF gain of 15 dB,an amplifier bandwidth at about 70 nm and the maximum gain ripple less than 1.2 dB have been achieved with 4 pumps by using the optimization of the ISAA. Comparing with other existing methods,the ISAA can attain a required low gain ripples and larger bandwidth without any gain flatten filter.