On-orbit capture by space robots is one of the main modes of spacecraft on-orbit servicing. For space robots capture of uncontrolled rotating satellites, the 6-DOF synchronization control approach strategy is investigated to improve the time horizon to suit grasp. Firstly, the target motion model is provided, and the attitude is described by modified rodrigues parameters. Then suppose that the attitude control of space robot is actuated by momentum wheels, the 6-DOF synchronization control is conducted in two phases: translational control and rotational control. In consideration of the uncertainty in inertia parameters, the control laws for translational and rotational synchronization are derived respectively by adaptive output feedback control. The simulation results show that the models and algorithms are efficient under the condition of unknown bounded disturbances and inertia parameters uncertainty.