Abstract: Adopting noise-initiation mode of stimulated Brillouin scattering(SBS),the transient SBS equations are numerically solved,and the intensity distribution of transmission beam when the Gaussian beam passes Brillouin medium is simulated.The results indicate that the peak intensity of transmission beam is limited,and the cross-section intensity distribution is approximately flat-topped super Gaussian,which shows the optical limiting effect of SBS.When the interaction length or gain coefficient is changed,the SBS threshold is changed,and the intensity value of optical limiting is altered.