In order to improve space positioning accuracy of the Agile Wrist consisting of a modified spherical parallel manipulator, which will influence the result of the Collisions in a robotic mechanical testbed directly, this paper explores the motion control of Agile Wrist.Based on analysis an input-output (I/O) equation of spherical four-bar linkages for forward-displacement of spherical parallel robots, the inverse kinematics derivation is reported here to find the active-joint variables for each possible position and orientation (pose) of the mobile plate, as well as the singularity exist and defines what may be generalized as the workspace boundary.Meanwhile the kinematics simulation by using simulink S-Function combined with Q8 controller was carried out.The results showed that the Kinematics analysis and Control Design of Agile Wrist were correct.The modified spherical parallel manipulator can meet with the demands of Collisions experiment in the robotic mechanical testbed.