Abstract: The intensity and angular distribution of Brillouin scattering have got much attention with the development of light scattering detection technique,especially in ocean detection with Brillouin scattering.The Brillouin scattering cross section is deduced with classical electromagnetic theory,and improved when we combine quantum electrodynamics with classical electromagnetic theory.At last,both ways in depicting the physics process of Brillouin scattering underwater are compared and discussed intensively.