This paper is concerned with the fundamental theory of the ray tracing method(RTM)for its application to the wave scattering by two kinds of rough surfaces, one is smooth like sea surfaces and the other is rigit like buildings in urban area. We use Fresnel's reflection coefficients in connection with reflected rays, and for diffacted rays, we employ the approximate diffraction coefficient of the nife edge diffraction. First we check the accuracy of the diffraction coefficient by comparing its results with the analytical solutions based on the Wiener-Hopf technique(WHT). It is shown that we two results are in good agreement. Finally we show some numerical examples of reflected and diffracted rays with regard to the two types of rough surfaces.