This paper proposed a new method of features description for target recognition and insulator recognition of the actual aerial images. Firstly, a method of calculating the difference was defined. The gray value matrix of an image was converted to a difference value matrix. The non-linear relationship between human eye sensitivity and differences of image gray value changed into a linear relationship. Then the difference value, shape, angle and other features of a region and the combined features between regions were described. Experiments showed that the proposed method can represent multiple features of image such as the gray differences, the shape changes, and so on. The new method was applied to describe the actual aerial images, and achieved the recognition of insulator.