Abstract: This paper discusses control problem of dual-arms space-based robot system with unknown payload parameters to track desired trajectory in inertial space, when the attitude of base is controlled and its location is uncontrolled. Referring to the principle of linear momentum conversation and the Lagrange approach, the full-controlled dynamic equation and the Jacobian relation of space-based robot system with dual-arms are established. Then, for a space-based robot system whose dual-arms system has unknown payload parameters, a composite control scheme is designed on the base of a computed torque controller and a fuzzy compensator to track desired trajectories in inertial space, i.e., balancing the effect of system unknown payload parameters on computed torque controller with fuzzy adaptive compensator, in order to ensure the whole closed-loop control system asymptotic stability with the existence of unknown payload parameters. The mentioned control scheme can effectively overcome the effect of system unknown payload parameters and control both the base attitude and the end-effector of dual-arms space-based robot, so to track the desired trajectory in inertia space. The advantages are obvious: neither the mentioned control algorithm needs to measure and feedback the position, velocity and acceleration of the floating base, nor it requires the dynamic equations of the system inertial parameters to be linear. The simulation results show that the proposed control scheme is feasible and effective.