[en] This paper presents our study of stimulated backward Raman scattering (SRS) and stimulated backward Brillouin scattering (SBS) instabilities, which appeared when the pump laser passed through the hohlraum plasma in the indirect driven inertial confinement fusion (ICF). It mainly introduces the physical model of the spectral analysis code in detail and the simulated processes of SRS and SBS under different plasma parameter conditions. Influence of hohlraum plasma parameter on spectral characteristics of SRS and SBS are analyzed, and the beneficial parameters to restrain the instabilities are presented, which provide references to the relevant target design. (authors)