The invention discloses an optical parallax acquiring method, an optical parallax acquiring device and an optical parallax acquiring system, relates to the stereoscopic vision technology, and can reduce a search range for stereoscopic matching obviously, reduce calculated amount in the process of acquiring the optical parallax and improve the overall performance of the system. The optical parallax acquiring method comprises the following steps of: performing key point extraction on a first image and a second image respectively to acquire first image key points and the second image key points;performing stereoscopic matching on the first image key points and the second image key points to obtain corresponding matching points of the first image key points in the second image key points; and calculating the optical parallax of the first image key points and acquiring an optical parallax map according to the optical parallax. The method, the device and the system are suitable for opticalparallax acquiring scenes in any stereoscopic matching.