Abstract: An iterative method for unstructured dynamic-grid using springs based on LU-SGS (lower-upper symmetric Gauss-Seidel) is presented to reduce time of iterative in dynamic discontinuities simulation. Dynamic grid iterative time is as much as time of field itemtive as shock and flex-wall are numerical fitting by time-dependent Euler equations, because dynamic boundary is moving and whole unstructured grids are updated in every step of field iterative. A sparse matrix mapping grid topology based on spring strategy is presented. LU-SGS strategy is used in numerical simulation and dynamic grid is managed in order to solve the time choke point. Numerical results show that LU-SGS iterative method can be used to dynamic discontinuities fitting by implicit scheme. The presented method decreases more than 20% iterative time than classical SOR method.