The present invention relates to a method for merging regions in the image/video, capable of merging plural of image regions into an image merging region. In the disclosed method, these image regions are first sequenced basing on their compactness value. Then, one of these image regions is designated as a reference image region, and a merging test process is executed by merging the reference image region with one of the nearby image regions thereof in sequence, for forming a temporal image merging region. Later, the compactness value of the temporal image merging region is compared with the compactness value of the two consisting image regions thereof, respectively. When the compactness value of the temporal image merging region is larger than either one of the compactness value of the two consisting image regions thereof, the temporal image merging region is designated as an image merging region.