Abstract：There are some shortcomings for the fog fuzzy image, such as the low contrast, blurred, and poor effects after the mathematical morphological enhancement. A new image clearness algorithm based on the fuzzy contrast and mathematical morphology is described. Using the previous fuzzy contrast enhancement algorithm, a new fuzzy membership function is defined, the image is changed from spatial domain into fuzzy field directly through it; therefore a fuzzy feature plane is obtained. In the fuzzy feature plane, the image could be enhanced. Lately, the image is taken back to its spatial domain. Then it is combined with the top-hat transform and bottom-hat transform of mathematical morphology pre-treatment. Finally, the enhanced image is obtained. An experiment for the fog image is presented. The results show that the algorithm has higher contrast and better visual effects. It is quite obvious that the algorithm is able to raise the contrast at the border and background and improve visual effects. In the other hand, this algorithm is good at making fuzzy image details become clearer, the noise is also suppressed, and there is no over enhancement, particularly in the sky area. Therefore, the proposed algorithm is an effective algorithm to clear fog image.