Due to some specific conditions in engineering exploration, some previous theories and conclusions of surface wave have different degrees of limitations in application. In the light of the virtual work variation principle of elastic dynamics, the present paper, when emphatically analysing free surface energy source provided by external forces, introduced the concept of equivalent surfauce wave (energy) seismic focus. Then, with finite element method, the frequency divergent equation of Rayleigh surface wave for half-space multiple nonhorizontal layer media was established. The work contributes to the development and improvement of the surface wave theory and its applied technique.