Pulse laser with 50 MW maximum peak power and wavelength of 531.81 nm is used to pump 500 m silica single mode fiber (SMF) in order to induce the stimulated nonlinear effect. Based on the nonlinear optics theory, optical fiber transmission theory and experimental measured data, effect of the four-wave mixing (FWM) on the spectral structure of stimulated Raman scattering (SRS) is studied. And the transmission modes of SRS and FWM in the silica SMF are also presented. Research results show that in the silica SMF, FWM effect is able to induce the low order Stokes light of SRS to produce additional peak spectral lines. Meanwhile the spectral broadening effect of the high order Stokes spectral lines of SRS can also be produced, and this could finally lead to frequency shift of the high order Stokes spectral lines of SRS.