After the coupling equations of co-pumping,counter-pumping and bidirectional-pumping distributed Raman amplifiers(DRAs) are theoretically analyzed,the power distributions of these three DRAs are acquired with numerical analysis.The performance factors,such as net gain(NG),amplified spontaneous emissions(ASE) noise,double Rayleigh backscattering(DRB) noise,noise figure(NF) and optical signal noise ratio(OSNR),are discussed in depth.It can be found that the NGs of the three DRAs are almost equal.The counter-pumping scheme will induce higher ASE.And the co-pumping DRA has greater DRB noise,but its NF and OSNR are both better than the others’.Furthermore,the relations between signal power and NG,NF,OSNR are also investigated.It is shown that the NF and OSNR of the co-pumping scheme are superior to those of the other two schemes at small input signal power.The above conclusions can play a very important role in guiding the optimum design of DRA. After the coupling equations of co-pumping, counter-pumping and bidirectional-pumping distributed Raman amplifiers (DRAs) are theoretically analyzed, the power distributions of these three DRAs are acquired with numerical analysis.The performance factors, such as net gain (NG) , amplified spontaneous emissions (ASE) noise, double Rayleigh backscattering (DRB) noise, noise figure (NF) and optical signal noise ratio (OSNR), are discussed in depth. It can be found that the NGs of the three DRAs are almost equal The counter-pumping scheme will induce higher ASE. And the co-pumping DRA has greater DRB noise, but its NF and OSNR are both better than the others. "Morerther, the relations between signal power and NG, NF, OSNR are also investigated. It is shown that the NF and OSNR of the co-pumping scheme are superior to those of the other two schemes at small input signal power. The above conclusions can play a very important role in guiding the optimum design of DRA.