Accurate and fast positioning of large aircraft component is of great importance for Automated Alignment System. The Ball joint is a widely-used mechanical device connecting the aircraft component and positioners. However, there are some shortcomings for the device in man-machine engineering, such as the entry state of the ball-head still needs to be confirmed by the workers and then switched to the locking state manually. To solve above problems, a new positioning mechanism is present in this paper, which consists of a ball-head and a ball-socket. The new device is equipped with a monocular vision system, in which a calibrated industrial camera is used to collect the images of the ball-head. And then, the 3-D coordinate of the ball-head center is calculated by a designed algorithm, guiding the positioner to capture the ball-head. Once the ball-head gets into the ball-socket, the pneumatic system will drive the pistons to move to the specified location. Meanwhile, the amount of compression of a set of springs has changed, so the steel balls are compelled to compress, contact or separate the ball-head, which means the states can be switched automatically. At last, an experiment is carried out to verify the accuracy of the visual system by comparing the measurement results with the laser tracker. The experimental results indicate that the design of the new positioning device with ergonomics can not only reduce the labor intensity, but also improve the assembly efficiency.