In order to realize the real-time pose determination of the flotation experiment platform, a pose measurement method based on monocular vision was proposed. Firstly, an easily identifiable circular cooperative target was designed, which was invariant to the rotation, translation and scaling. Then, combining the size, shape and installation location, the cooperative target could be detected fast based on Blob analysis which could ensure the accuracy of the point extraction. Next, a method was proposed to extract the object circle centers fast and robustly by scanning the connected domains to be recognized. Finally, the actual pose of the flotation experiment platform could be calculated by the circle centers in the computer image coordinate system and the relations of coordinate transformation of the vision-based pose measurement system. The results showed that the proposed method had high accuracy and strong anti-noise capability, and the average period of processing the image of 1 600 pixel×1 600 pixel was 53.086 ms (about 19 frames per second). The method can realize the real-time, accurate and robust measurement of the pose of the flotation experiment platform.