Researches indicate that the gray-scale images mapped from most nature objects accord to the fractal Brown stochastic field which foundation is self-similarity, an image is self-similarity means the image is made up of copies of itself in a reduced scale. The fractal dimension can quantificational depict the fractal character and the property of an image. Therefore, a new method based-on fractal dimension to fuse mid-wave infrared images and long-wave infrared images is presented in the paper. First, images are decomposed into different scale using wavelet transform. Second, the fractal dimensions of sub-images of original images are computed, and then take them as weight to fuse sub-images at the same level according to different direction. Finally, reconstruct the fused images by wavelet inverse transformation. The experimental results imply that the method can effectively preserve the information of source images with a high contrast and may be very practical.