Battle Damage Assessment (BDA) is to assess the damage degree of enemy’s target after being attacked. In modern war, combat commanders always make decision on the basis of BDA. In this paper, an automatic method for assessing the damage extent of an attacked airport based on the image taken before and after a strike is described. Firstly, the airport blockade condition is analyzed and damage assessment criteria of airport are proposed. Secondly, three steps of the image information pretreatment are carried out and a reliability analysis method of image information is proposed. Lastly, damage assessment result is calculated to verify the validity and availability of the proposed method.