A scalable visual measurement was presented to meet the technical requirements of target location under large size and long distance non-contact conditions. Many visual measurement methods seek to obtain higher accuracy on the improvement of PnP algorithm, but do not consider the impact of increasing the number of feature points. Thus, a cooperative target design by quantitatively expanding the number of feature points to achieve higher positioning accuracy was proposed. Firstly, through the establishment of measurement model and accuracy analysis, the function analysis formula of measurement accuracy of n-point target was obtained by using error propagation theory. Then the accuracy of the model was verified through simulation experiments, and the effect of the arrangement of the feature points of the cooperative target on accuracy was further discussed. Subsequently, the target layout and structural parameters were optimized. The experimental results show that the reprojection error of the designed 16-point ring array target is reduced by about 50.3% compared with the same size P4P target, and the stereo target further reduces the reprojection error by 39.2%. This technology can be used not only for target positioning in special environments, but also for unit state monitoring in complex systems.