The invention discloses a single image defogging method based on a luminance dark priori method and bilateral filtering. A new image priori method, the luminance dark priori method, is used for estimating the fog concentration and restoring an image, the priori method is based on the statistical law of fog-free image HSI color space luminance components, and according to the statistical law, some pixels exist in local areas of most fog-free images, and the strength value of the luminance components I of the pixels is low and approaches to zero. Based on the priori method, the image is firstly transformed to the HSI color space to obtain the luminance components, a dark priori image is calculated, then atmosphere light and transmissivity are estimated through the luminance dark priori method, the transmissivity is refined through the bilateral filtering, and finally restoration is carried out according to an atmosphere scattering model to obtain the fog-free images. According to the method, the contrast ratio of the image is enhanced obviously, grain details in the images are restored, the visual effect of the image is obviously improved, and the good algorithm performance is achieved.