Abstract:Finite element method has been practically applied to the forward modeling of elastic wave,But its shortcomings,such as large storage needed and slow calculation,remain,It is noted,after a detailed analysis of finite element algorithm,that both stiffness matrix and coupled matrix are symmetrical in special elements,the coupled matrix having transposition character and some specific characters,Square element is used,and the elements multiplied by nodes are merged into discrete time operation,thus .doubling the calculation speed but halving the storage of global matrixes,An example is given to prove that the fast algorithm is feasible.