To reduce inertia of moving links into resultant force and moment vectors and to represent center of mass as node in finite element models are widely-used in mechanical calculations of linkage mechanisms. Considering distributed inertia of motion makes possible to create more precise finite element models in spatial linkage structures. By algebraically summing all the distributed inertial loads acting in both directions, perpendicular and along the axis of a constant cross section link, we can show that their intensity varies linearly along the length of link. Using this approach together with Chasles theorem for a point of free rigid body in projections onto the moving axes in the finite element method for rectilinear homogeneous rod, we reach to a more precise finite element model considering analytically distributed inertia of motion. Besides, we obtained subvectors in matrix relation which binds the generalized reaction forces acting at the contact points of the rod element with nodal generalized elastic movements. These subvectors includes the weight and inertia of a distributed spatial movement of link.