Abstract:The relationship between the scattering wave field(primary wave field) and the turbulence of medium parameter is determined under prerequisite of Born's approximation. The approximate formula of reflection coefficient can be deduced by solving the coefficient-varying Green's function with the use of discrete-grid ray tracing method. By using discrete-grid ray method based on Huygens' principle and Fermat's principle,the corresponding ray model is developed to achieve the algorithm for solving reflection coefficients. Then approximate wave impedance is computed after background velocity has been obtained by making constant-velocity scanning. This ray tracing method is particularly applicable to prestack seismic data and integration algorithm because it is not affected by dimension number,trace gather form,prestack(or poststack)processing.