When an air-to-ground guided missile captures the infrared image at the terminal phase of guidance, the gained infrared images are bad in image contrast, blurry, large yawp because of the restriction of infrared imaging component and the radiation of atmosphere. Based on the problems, the multi-scale Retinex algorithm was applied to the air-to-ground guided missile's infrared image enhancement, and the corresponding method and flow were given. An improved algorithm was explored for the defects of the multi-scale Retinex. The result of the experiment shows that the improved algorithm has good effect on ameliorating infrared image hue, contrast, details and yawp removing, and which can enhance the precise hitting capability of the air-to-ground guided missile.