Abstract: Automatically selecting seam line,which should not cross buildings,trees,higher than ground,and the area with big gray difference between overlapping orthophotos,is important for seamless mosaicking and automated production of digital orthophoto maps(DOM).An automated seamline detection method for orthophoto mosaicking based on ant colony system is introduced.The experimental result shows that this method can select seamline of orthophoto image with great speed and high accuracy,and realizes DOM automatic seamless mosaicking in surveying and mapping production.