An　essential　dispersion　relation,　which　can　describe　the　dynamic　properties　of　stimulated　Raman　scattering　instability　as　a　laser　beam　propagates　through　plasmas,　is　derived　analytically.　The　development　of　growth　mode,　angle　distribution,　and　temperature　dependence　of　the　instabilities　are　presented　by　solving　this　dispersion　relation　numerically.　A　significant　dynamic　characteristic　has　been　revealed　that　the　temperature　increasing　of　the　electron　would　result　in　redshift　of　scattered　spectrum　at　high　laser　intensities.　Furthermore,　a　novel　modulational　instability　with　double-peak　temporal　structure　appears　in　a　limited　density　region　because　of　the　coupling　of　scattered　upshift　and　downshift　waves.