In　this　paper,　the　sliding-mode　variable　structure　control　problem　of　a　free-floating　space-based　manipulator　system　whose　base　attitude　is　controlled　is　studied.　With　the　linear　momentum　conservation　of　the　system,　the　kinematics　and　dynamics　of　the　system　are　analyzed.　It　is　demonstrated　that　the　dynamic　equations　and　kinematics　Jacobian　matrix　of　the　system　can　be　linearly　dependent　on　a　group　of　inertial　parameters.　In　order　to　make　the　control　scheme　more　effective,　an　improved　sliding-mode　variable　structure　control　scheme　for　space　-based　manipulator　to　track　desired　trajectory　in　workspace　is　developed　with　the　results　proposed　above.　The　control　scheme　proposed　need　not　calculate　the　elements　of　Centripetal　and　Coriolis　torque　vector　time　and　again,　by　off-line　estimating　the　upper　and　lower　limit　of　the　elements　only　one　time.　So　It　can　effectively　reduce　the　calculation　time　needed　by　the　classical　variable　structure　control　scheme　during　the　period　of　real-time　control.　A　simulation　study　of　two-link　planar　space-based　manipulator　system　is　presented,　it　is　shown　that　the　control　scheme　proposed　is　feasible　and　effective.