Since Mie model and Debyeseries expansion model can not accurately explain the back scattering phenomenon of large dimensional bubbles in seawater when the size of the bubbles reaches micron order of magnitude and their calculation speeds are slow, a geometricalphysical optical model is put forward. The numerical calculation method of the scattering property for the large spherical bubbles, based on geometricalphysical optical model, is described. In comparison with Debye model, the calculation result of the geometricalphysical optical model agrees with Debye model basically. The calculation process of the method is independent of size parameters, and it is more stable and faster than the traditional methods based on LorenzMie theory or Debyeseries expansion. Some calculation results for the angular distributions of the scattering intensity are also given.