1. A device for determining a disappearing direction, the device comprising: a moving target detecting unit configured to detect in a plurality of video images a moving target area where a moving object locates; a feature point extracting unit configured to extract at least one feature point on the moving object in the detected moving target area; a moving trajectory obtaining unit configured to track a movement of the feature point in a predetermined number of video image frames to obtain a movement trajectory of the feature point; and a disappearing direction determining unit configured to determine, according to the movement trajectories of one or more moving objects in the video images, a disappearing direction pointed by a major moving direction of the moving objects.