An unrepeated transmission system of 4×100 Gbit·s -1 over a span loss of 68.85 dB is realized by the bi-directionally pumped Raman amplifier (BDPRA) scheme. The optical signal to noise ratio, transmission margin, and bit error ratio of this system are tested. The power evolution of this BDPRA in the 4×100 Gbit·s -1 transmission system is simulated. The research results show that the signal input power, forward/backward Raman gain distribution and cost should be comprehensively considered in the applications of the BDPRA scheme.