A vectored thruster based on 3-RRRR parallel manipulator for small-size AUVs is designed to solve some drawbacks of conventional AUVs, which the control surfaces become ineffective at zero or slow forward speeds. Though this method, the thrust from duck propeller is controlled by the parallel manipulator. This approach has advantages of high stiffness, high mobile and large payload capacity. The parallel manipulator is analyzed in kinematics and is emulated in MATLAB to verify the performance of the vectored thrust control system. The vectored thrust control system designed in this paper with high rapid response capabilities is an effective method to expand the application range of small-size AUVs.