Abstract: The fusion of infrared (IR) and low-level-light (LLL) image offers observers more image information, but it also covers up some target information because of too much background details. To match abundant background information with target enhancement, a kind of imaging fusion algorithm was proposed in the paper. It improved the algorithm on top-hat transformation to enlarge the target information of infrared image, and meanwhile removed some redundant background details. Considering eyes'sensitivity to color, it mapped LLL and IR image into color space with color mapping formula, and then fused. The result shows this algorithm not only enriches background details, but also enhances the important target information.