Abstract: Dynamic analysis methods For structures arc generally divided into two kinds: multi rigid-body dynamics, finite element method. The former is used to analyse multi-rigid-body system, the latter is used to analyse elastic system. In dynamic analysis of the combined system of multi rigid-body and elastic body, many problems awaiting solution In this paper the improved finite element method is presented and applied to the analysis of not only clastic system, but also multi-rigid body system, and their combined system.