In order to achieve fast and high-precision position switching control of a ground-based telescope， without overshoot and while improving the positioning performance， a trajectory-planning strategy based on an approximate optimal-command-shaping algorithm is proposed. The approximate optimal-command-shaping algorithm is utilized to design the command shaper， which is located before the position controller. The designed command shaper is able to perform trajectory planning， using the reference command， and the speed- and acceleration-limit information of the system. As a result of the algorithm-designed command shaper， the system can be guided to its destination quickly and smoothly. Compared to the traditional trapezoidal-command-shaping algorithm， the proposed approximate optimal-command-shaping algorithm overcomes the problem of chattering， thus achieving better position-control performance. The experimental results demonstrate that， compared to the positioning strategy without trajectory planning， the system using the proposed positioning strategy has a reduced adjustment time. In particular， the adjustment time for the system to enter the 2″ error band in response to a 2.5° and 30° step reference is reduced by 1.14 s and 1.57 s， respectively. In addition， the overshoot of the position response is significantly reduced. The simulation and experimental results show that the positioning performance of the telescope can be improved effectively by the trajectory-planning positioning strategy， based on the proposed approximate optimal-command-shaping method.