Abstract: In this paper, a relative coordinate system is introduced to describe the motion of flexible multibody system. This coordinate system fully utilizes the property of transform matrix to reduce the nonlinear couplings between rigid and elastic motion. A recursive formulation for the dynamic analysis of open loop trees deferrable multibody systems based on the Jardon s principal is presented. The dynamic equation is assembled from outer layer to inner layer. Having used the recursive technique for dynamic equation s formulation, computer storage is much less than other methods in calculation. A numerical example is given.