IR imaging guidance technology that adopts Focal Plane Array (FPA) has been widely used in airtoair missiles by reason of its predominant capability. On the surface of aircraft, different parts are at different temperature, so the different parts of target image are different in grayscale. It will cause difficulty in accurate target segmention. Based on the features of aircraft IR image and the purpose of IR image segmentation in imaging guidance technology for new airtoair missile, a novel segmentation algorithm that is beneficial to target features recognition is proposed. The target image is segmented firstly. Then the areas which are inside of the target image are filled by selecting the suitable structural elements and utilizing the parallel characteristics of mathematical morphology. Finally, the accurate result of segmentation is obtained. The segmentation result of this method is of great help to grayscale continuity based on feature recognition algorithm.