Based　on　the　linearized　differential　relationship　in　a　closed-loop　linkage　payload,　the　kinematic　and　dynamic　coordinated　constraints　of　the　whole　system　are　derived.　The　system　dynamic　equations　are　then　developed　for　the　first　time　by　using　finite　element　method　and　Lagrange　equation.　A　numerical　example　of　the　inverse　dynamics　of　two　planar　3-R　flexible　robots　manipulating　a　four-bar　linkage　to　realize　the　kinematic　planning　task　of　the　objective　is　illustrated　successfully.