Abstract: The three-dimension dynamic equations of tethered satellite systems, with the mass of the tether considered, are formulated. The tension control rules and the optical relieving speed of the tether are derived by Pontryagin's method. A libra-tional motion of deployed system about the local vertical is studied. The movement couple between the center of mass and the attitude of tethered satellite systems is discussed, when the center of mass moves along Keplerian orbit. The numerical simulation results are included.