This paper proposes an equivalent second order elastic wave equation to solve the problem of being unable to completely

separate the coupled P and S wave by full elastic wave equation. Through solving this equivalent wave equation by high-order

staggeredgrid finite difference scheme together with Flux Correction Technology (FCT) and separating wave fields of the

isotropic model and layered model, the authors accurately obtained the hybrid wave field and completely separated fields of pure

P wave and pure S wave fields. An analysis of the numerical results shows that the method is effective and reliable in isotropic

media, and there exists abundant energy transform information in separated pure P and pure S wave field. The result of the study

is of significance in understanding the propagating law and the elastic wave theory in the complex wave field.