Abstract: For the space camera on orbit active optics requirement, the position and orientation of secondary mirror relative to the primary mirror need to be adjusted. Based on the parallel robot joint space method, the motion control system of 6-PSS Stewart platform secondary mirror adjusting mechanism was designed. By use of DSP and FPGA as the core processor, linear encoder as the feedback element and the integrated three-phase bridge as driving element, the motion control circuit was completed. Based on the top level inverse kinematics model and the bottom level link control system, the motion control algorithm of the secondary six DOF adjusting mechanism was accomplished, the control parameters were easy to be adjusted and the algorithm was easy to be used in the engineering, the requirement of high reliability adjustment for space motion mechanism was satisfied. Experimental results indicate that the 0.7 m and 3 motion accuracy can be achieved, the demand of space camera active optics can be satisfied.