In order to cope with the pose duality problem in the visual measurement of a single circle, a disambiguating approach is proposed utilizing constraint angles motion reconstruction. On the premise of camera calibrated, the pose parameter of a circle is estimated from its projected ellipse curve but the pose has duality. The world coordinates of feature points are recovered by the method of multiple view structure from motion and constraint angels are reconstructed with feature points. Based on the nature that rigid body motion does not change space angles, the poses of multiple view are determined simultaneously. Experimental results indicate that within the range of 500 mm the circle radius, the success rate of eliminating false solution is up to 100% when the noise level is within 0.4 pixel and 93% when the noise level is 1 pixel. And the success rate is 99.6% when the noise level is 0.1 pixel and the range is 1000 mm the circle radius. Besides, the average run time of the proposed algorithm in two views is about 5 ms which suits real-time application. The proposed approach can effectively identify real poses of a single circle in real time without any additional information of target.