Aiming at the low efficiency of traditional projectile image interpretation, an image automatic interpretation method based on improved edge detection has been proposed to obtain the coordinates of projectile feature points. Roberts template is used to calculate the image gradient at the sub-pixel level, and the maximum gradient in the neighborhood is found as the anchor point. The single pixel edge of the projectile is obtained by the Smart Routing method and the centroid coordinates of the projectile are obtained by moment theory. Using the resolution plate to test the improved edge detection method, and the projectile centroid in shadow image is obtained. Experimental results show that, compared with the traditional method, the improved algorithm has better effect on edge continuity and positioning accuracy, and the error of the projectile centroid’s abscissa is reduced from 6.7 % to 2.8%.