Stimulated Raman Scattering (SRS) effect is a key factor restricting the application of high power laser transmission over single mode fiber in long distance . Using 1550nm unpolarized continuous wave single-mode fiber laser as light source, stimulated Raman scattering phenomenon generated by 103km single-mode fiber transmission under different injected light power conditions is experimentally studied. Cascaded long-period fiber gratings are used to carry out stimulated Raman scattering suppression experiments, and corresponding theoretical analysis is carried out. A criterion for the effectiveness of fiber stimulated Raman scattering suppression is proposed. Experiments demonstrate the stimulated Raman scattering phenomenon and verify the effectiveness of cascaded long-period fiber gratings for the suppression of stimulated Raman scattering.