Abstract: Aiming at the special situation of positioning and identifying multi-targets in air, this paper has the advanced invariant moment arithmetic to carry out. Because the moments request good quality of identifying, so this paper provides a new morphological gradient image edge detection operator which can estimate orientation, and proves them in theory and practice. There are four element structures with different direction. In these operators, the blurring processing is added, it makes that the operators not only depress the noise in image, but also enhance edges definition. And then it changes the edge detection image into the binary image through the optimal threshold segmentation. It also shows a new simple arithmetic about jointing broken lines. It does not only make the targets contour smooth, but also can find the single pixel boundary with tracking. Through kinds of tests, the identifying rate has been improved, and the dependability has been strengthened.