Vibration rejection is a key technology of telescopes with stable accuracy of μrad level. Due to the low-rate sample and large time delay of the image sensor, the conventional control loop cannot well mitigate vibrations, especially the wideband vibrations with wide range and large energy. On the concept of optimal force design, an improved wideband vibration rejection method based on Youla parameterization is proposed to mitigate vibrations for improving the closed-loop performance of telescopes. In the case that the disturbances frequency can be obtained, this method can mitigate wideband vibrations by designing an appropriate Q-filter to accommodate to the wideband vibrations. The simulation and experimental results show that the proposed method greatly improves the wideband vibration rejection ability and closed-loop performance of the system compared with the traditional proportional- integral control method. In addition, this method can be extended to many engineering projects because of its low dependence and easy implementation.