Giant telescopes with extremely large aperture widely adopt segmented mirror active optics technology, so active adjustment mechanism of displacement is one of the critical techniques. A novel 6-DOF mechanism featuring structural compactness in size and partial decoupling in degrees has been proposed as a potential supporting mechanism for sub-mirrors. It is of important significance to carry out profound study on the control strategy for large scale use of the 6-DOF adjustment mechanism in a highly segmented giant telescope. This paper presents first the control system design for a prototype of the 6-DOF mechanism and further the control strategy modeling for the future large-scale application of the mechanism in giant telescopes. The control system implemented for the prototype mechanism has been successfully tested by photogrammetry at lab. It provides closed-loop control and real-time measurement of all motors of one 6-DOF mechanism and is proved to be a system of high precision and efficiency. Afterwards, we explore and extend the control design of the novel 6-DOF mechanism to large-scale use in all sub-mirrors in a giant telescope. The principle, constitution, control algorithm and realization are covered and commented. The study and experiment carried out in this paper are also informative for the control of parallel manipulators in other industries.