Abstract: According to the elastic wave equation of motion,a decomposable matrix solution could be derived if the medium density,the Lame’s constants and the source signature are all meet the demends as the 2-D function required. In such case,the displacement vector matrix and the potential vector matrix of the earth surface elastic wave can be built up,and the decomposable matrix of the elastic wave could thus be obtained. On condition that the displacement vector, the density of the receiving points,the Lame’s constants,the spread direction as well as the strike of structure and formation are known,the longitudinal wave (P-wave) and the transverse wave (S-wave) could thus be decomposed. The algorithm recommended for wave decomposition is practical and effective,and is easy to carry out and fast in calculation. It is,In practice,suitable for any of the isotropic heterogeneous medium,and has been proved through modelling and field data processing. By using the algorithm, the interference betwwen the P-wave and the S-wave could be eliminated and the resolution as well as the continuity of the event could also be Improved.