Abstract: An adaptive controller is proposed for a space robot system with unknown payload parameters. The dynamic equations of dual-arm space robot system are derived through the Lagranian formulation. The obtained dynamic equation can be represented by a group of inertial parameters. Based on the results and recognizing the payload parameters are unknown, an adaptive controller is designed for the robot system to track the desired trajectory. In particular, neither the position, the velocity are required, nor the acceleration of the base. Finally, the numerical simulation is carried out, which confirms the controller proposed is feasible and effective.