Abstract: in this paper, d'Alembert-Lagrange principle is used for modeling a system consisted of a base, (n-1) rods and a load at the tip which connects each other with hoes.Numerical simulation based on the Gear algorithm is applied to the 3-D manipulator system used in the space technology, which is consisted of one rigid rod, two flexible rods with rigid load.The results of numerical sedation are satisfactory. In the case when the mathematics model of the flexible multibody systems is corresponding to stiffness ordinary differential equations,the method for the solution of the numerical sedation of the flexible multibody systems,especially for the 3-D systems,can be applied effectively.