Abstract: The concept of coherent coupling of optics and mechanics is presented here and its mechanism is analyzed. The coupled wave theory of nonlinear optics is adopted to establish nonlinear dynamics model describing generation and evolution of coherent acoustic wave in optical materials. The stress induced by SBS process is calculated in steady state case and the damage threshold theory for transparent materials is presented to study the dependence of damage threshold on Stokes laser fluence.The research shows that the SBS induced stress would cause material breakdown which most probably happens in the entrance surface of pump laser, and the Stokes laser does not play an important role in the damage thresholds in steady case. Finally, the future work is outlined to promote the study on coherent