An optimized Digital Background Propagation（DBP）algorithm is proposed and experimentally demonstrated in a bidirectional Raman amplification unrepeated system.The algorithm is achieved by reversely solving the Schr9 dinger equation in electrical domain

which can compensate both chromatic dispersion and nonlinear effects.The proposed algorithm is implemented by optimizing the power curve.An unrepeated transmission of a 10 Gbaud/s Quadrature Phase Shift Keying（QPSK）signal over 320 km single mode fiber is experimentally demonstrated.The experimental results show that the performance is improved by 0.7 dB to 1 dB based on optimized DBP algorithm.