In order to achieve the high motion precision of the macro-micro parallel manipulator system for a large radio telescope, its real-time motion planning is dealt with in this paper. To uniquely determine the spatial position and orientation of the cable driven parallel manipulator, the real-time optimization is conducted according to the principle of uniform tension in the six driving cables. Synchronized points and the “judge and wait” mechanism ensure the continuity and synchrony of the trajectory tracking of the two parallel manipulators. The preadjustment of the micro parallel manipulator reduces the drastic dynamical coupling as a result of the fast movement of the micro manipulator. Besides, over-workspace avoidance procedure is introduced to restrict the micro parallel manipulator not to exceed it workspace. Experimental results validate the high precision of the macro-micro parallel manipulator system with supervisory controller and the motion prediction algorithm.