Image processing was used to realize automatic collimation ofmissile. For the complex background of directional norm pole, the method of color segmentation p layed an importantrole. Norm pole pixelswere segmented by the character of red weight and the ratio of red weight to blue weight. The characters of area and perimeterwere used to make norm pole pixels nonzero value. Automatic collimation of norm pole was realized by precisely halving norm pole on the method of subp ixel on former gray image.