Numerical simulation was performed to study the stimulated Brillouin scattering(SBS) amplifier of self-Stokes-seeding. Chracteristic parameters such as Stokes laser,energy reflectivity,evolvement and distribution of maximum stress,pulse compression and SBS fidelity in fused silica were discussed for different Stokes ratio,wavelength,energy,pulse duration and interaction time.The focused Gaussia n pump laser was used.We got conclusions that the damage in near-front side of SBS medium was the characteristic of SBS; tuning parameters of pump laser, super -sonic stress formed in SBS process would damage the SBS medium not only on the front side, but also the damage near the focus;and the damage near the focus wo uld be made earlier when both parts were damaged.