An auto-convergence system includes a disparity unit, a convergence unit and an active learning unit. The disparity unit performs a disparity analysis upon an input stereo image pair, and accordingly obtains a disparity distribution of the input stereo image pair. The convergence unit adjusts the input stereo image pair adaptively according to the disparity distribution and a learned convergence range, and accordingly generates an output stereo image pair for playback. The active learning unit actively learns a convergence range during playback of stereo image pairs, and accordingly determines the learned convergence range.