To study the process and law of Raman scattering,at first,numeric simulation of the coupling equations of Raman scattering is provided,which demonstrates the transition of spontaneous Raman scattering to stimulated Raman scattering. The simulation results show that threshold is very important; Raman scattering spectrum presents three typical patterns when pump power is larger than threshold,namely that the pumping power and optical fiber length of scattering intensity peak is an inverse relationship; the maximum value of spectrum increase when pump power is larger; There widely exists the red shift of energy,including the same grade spectrum inside and between different grade spectrums. Then,the application of Raman scattering is deeply analyzed. The conclusions are helpful to the study and experiment work of Raman scattering.