Foreign object debris is one of the important factors that threaten the flight safety of the aircraft. To carry out automatic detection research of foreign object debris is an inevitable requirement to effectively ensure aircraft flight safety. Focus on detection of FOD, firstly an image difference method based on DGPS was proposed, this method used RTK to obtain high-precision position information of the image of runway and aligned two images in the same place to meet the conditions of image difference. Histogram for specification was also developed to complete brightness correction. Then FOD could be detected by image difference. Finally, experimental verification was carried out. Experimental results show that the method can effectively detect foreign objects debris on airport runways with no less than 2 cm×2 cm.