Abstract：Man-made boundary in forward computation and migration image using finite difference of wave equation must result in boundary reflection waves to damage the effects of forward computation and migration image.To cope with the problem,people have put forward various equations of absorbing boundary condition,which,however,give unsatisfactory absorbing effect.By using conjugate gradient method under the least square meaning,we get the optimized coefficients of absorbing boundary condition equation,so that the absorb- ing boundary condition equation approaches to inside equation as much as possible and boundary reflection waves can be absorbed all or part.Theoretical analysis and real migration indicate that our equation of absorbing boundary condition brings nice absorption of the waves incident upon boundary in various angles.
